Animal Deterrent Products Archives - Pigeon Patrol Canada

TransLink and BC SPCA tackling the pigeon problem

by Pigeon Patrol | Oct 15, 2024 | Animal Deterrent Products, Bird Netting, Bird Spike, Pigeons, Pigeons in the News, UltraSonic Bird Control

VANCOUVER, BC — TransLink and the BC SPCA are teaming up to humanely reduce the pigeon population at VCC-Clark SkyTrain Station. An automatic bird feeder is dispensing birth control for a pilot project to control the pigeon population. OvoControl is a non-toxic, effective and humane contraception used in other cities to prevent pigeon reproduction and reduce populations naturally through attrition.

Pigeons cause problems at several SkyTrain stations despite TransLink’s best efforts to control them. TransLink has:

Installed netting at stations to stop birds from getting into empty spaces
Set up spikes and strips to deter pigeons from roosting on flat surfaces
Hired a falconer to patrol stations with the most pigeons as part of another pilot project

Studies have shown a 50-90% population reduction in OvoControl managed pigeon populations. Pigeons that eat the bait pellets on a regular basis will not be able to fertilize eggs.

Dr. Sara Dubois, Chief Scientific Officer with the BC SPCA explains pigeons can breed rapidly but their urban lifespans are short. With fewer new pigeons born, the pigeon population around SkyTrain stations will reduce naturally and cause fewer operational issues, “OvoControl has been approved for use by Health Canada and only has contraceptive effects in birds. Pigeons must eat their daily dose (5g/bird) for the contraceptive to work, and it is designed to be fed in a manner to maximize pigeon feeding behaviour. We are happy TransLink is ready to partner with us and research what could be a very effective and humane long-term solution.”

Pigeon droppings are messy, but the birds also put customer safety at risk. Pigeons trigger track intrusion alarms, causing our driver-less trains to brake automatically. These hard stops can lead to customer falls and service delays.

TransLink customers and the public can help by not feeding the birds. Outside foods sources encourage birds to roost inside stations and can draw pigeons away from the contraceptive pellets. It is vital for the success of the project that people stop feeding pigeons in this area.

The OvoControl pilot may be expanded to other stations if successful at VCC-Clark.

The innovative partnership between TransLink and the BC SPCA has been supported by other local animal groups:

Linda Bakker, Co-Executive Director, Wildlife Rescue Association –

“The Wildlife Rescue Association of BC supports this new initiative to humanely reduce the pigeon population. Wildlife Rescue strives to reduce human-wildlife conflict in the urban environment and rehabilitates injured and orphaned wildlife. This project aims to humanely reduce the number of pigeons at areas that have a lot of potential casualties and injuries in pigeons. This project will reduce the number of injured, deceased and orphaned pigeons in these areas. Wildlife Rescue supports the BC SPCA in promoting humane wildlife management practices.”

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Two pigeons sitting together on piece of wood.

Michael Austin, Executive Director of the Vancouver Humane Society –

“While we continue to grow our wonderful city, it is important to consider the impact such developments have on urban wildlife; Vancouver Humane is pleased to support this initiative by TransLink and the BC SPCA to humanely control the pigeon population in order to reduce unnecessary suffering. We hope that other businesses can learn from this work and that more considerations are made for the non-human animals that live in our communities.”

TransLink is Metro Vancouver’s regional transportation authority and is the first North American transportation authority to be responsible for the planning, financing and managing of all public transit in addition to major regional roads and bridges.

Pigeon Patrol

Pigeon Patrol Products & Services is the leading manufacturer and distributor of bird deterrent (control) products in Canada. Pigeon Patrol products have solved pest bird problems in industrial, commercial, and residential settings since 2000, by using safe and humane bird deterrents with only bird and animal -friendly solutions. At Pigeon Patrol, we manufacture and offer a variety of bird deterrents, ranging from Ultra-flex Bird Spikes with UV protection, Bird Netting, 4-S Bird Gel and the best Ultrasonic and audible sound devices on the market today.

Canada’s top wholesaler for bird deterrent products for twelve consecutive years.

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Pigeon protesters ruffle Livingstone

by Pigeon Patrol | Oct 15, 2024 | Animal Deterrent Products, Bird Deterrent Products, Bird Law, Bird Netting, Bird Spikes

Mayor of London Ken Livingstone was unexpectedly “ruffled” on his trip to the US, by protesters opposed to his plan to reduce the number of pigeons in Trafalgar Square.

He was on a fact-finding mission to the US, but had not expected to be doused in water over an issue related to London’s most famous square.Mr Livingstone has been criticised after refusing to renew the licence of the last bird feed vendor in Trafalgar Square. Andrew Butler, a spokesman for the pressure group People for the Ethical Treatment of Animals (PETA) told how activists doused Mr Livingstone with a pitcher of water during a news conference in Washington DC on Thursday.

A protester shouted: “Your plan to poison pigeons is all wet. Mayor Livingstone starves pigeons to death.”

Pigeon on a roof with solar panels with pigeon spikes to repel pigeons, Darmstadt, Germany

Bird feed seller Bernard Rayner has until Friday to give up his job, after which the Greater London Authority will implement a one-month phased withdrawal of feed from the capital’s famous landmark.Mr Rayner had traded on a temporary licence since October after a High Court appeal against an earlier move by Mr Livingstone to target the pigeons.

At that time, Labour MP Tony Banks tabled a Commons’ motion in a bid to save the “gentle London pigeon”. Mr Butler said that people in the UK may be surprised about the trans-Atlantic interest shown in the issue – but the US activists feel strongly about the fate of the birds. He said: “This isn’t Hawaii. It’s freezing-cold concrete-covered London. There are no luscious fruit trees for the birds to flit over to. The baby and elderly pigeons have nowhere else to seek food.

“They’ll starve. What’s he going to introduce next? Bear-baiting? He is waging war against the symbol of peace. Pigeons are rock doves, and Ken needs to extend an olive branch.” The GLA plans to clean up the mess caused by pigeon droppings and pedestrianise the upper part of the square to make way for more cultural pursuits for visitors.

But Dr Jayne Cuthbert, a research fellow at Kingston University who has advised the government on pigeons, confirmed PETA’s fears that withdrawing the food supply will result in the deaths of thousands of the birds.

She said: “The basic law of ecology is that there will only be as many birds in any area as there is enough food to feed them. “The Trafalgar Square pigeons will therefore not be able to fly off elsewhere because there will be no food available.” The number of pigeons in British towns and cities is estimated to have doubled in the past five years.

Mr Livingstone spent the earlier part of the week in New York to find out about its public transport and urban regeneration schemes. He is now spending two days in Washington as a guest at the annual conference of US mayors

Canada’s top wholesaler for bird deterrent products for twelve consecutive years.

DAMAGE POTENTIAL

by Pigeon Patrol | Sep 25, 2024 | Animal Deterrent Products, Bird Deterrent Products, Bird Law, Bird Netting, Columbidae

Feral pigeons and certain species of gull, for example the Herring Gull and Lesser Black-Back Gull are potentially a source of risk to health and safety in the urban environment. A range of diseases have been shown to be carried by birds living in urban and suburban environments.

Pigeons and seagulls will deface buildings by their droppings deposited and nesting materials.

The feral pigeon use buildings throughout cities as a sheltered roosting site while waiting to feed at first light, on debris from waste management bins in the domestic and commercial sectors.

Both Herring Gulls and Lesser Black-Back Gulls are becoming an increasing problem in Dublin and surrounding areas, nesting on flat rooftops. They have become aggressively protective of their territory, especially during their breeding cycle.

Legal status

Unlike most other pest species, birds have legislative protection unless it can be provided that their presence is detrimental to man in some way.

Seagull flying in to to eat french fry chip.

Under the Wildlife (Amended) Act 2000 all wild birds, their eggs, nests and habitat are protected. However, member states may derogate from the provisions in the directive, where there is no other satisfactory solution, for the following reasons:

In the interests of public health and safety

In the interest of air safety

To prevent serious damage to crops, livestock, forests, fisheries and water

For the protection of flora and fauna

In Ireland, General Licences, issued and revised, annually by the Department list the birds that can be taken. The licences also state the reasons for such action, methods of control and that the work must be carried out by an authorised person (authorised person means the owner, occupier or someone authorised b the owner or occupier in writing).

These licences do not have to be applied for. They are a legislative means of removing the protection of certain birds, regarded as pests, from the general protection afforded them through the Wildlife (Amended) Act 2000.

Population control

Reduction in numbers by one of the approved methods, shooting, trapping etc will provide only short-term relief. This method should only provide temporary relief until proofing work is complete, or to clear derelict buildings of pest birds prior to demolition.

Management of pest birds can be divided into three distinct categories:

Reduction / removal of food sources

The number of birds in an area will be directly influenced by the food source available. Therefore, good waste management and discouraging members of the public from feeding the birds (mainly feral pigeons will naturally reduce the bird numbers over a period of time.

Removal of roosting sites

Design of new buildings should take into consideration ledges, windowsills and any other feature that might provide roosting sites for birds. An angle of 45 degrees or more will prevent birds from roosting. Maintenance of existing buildings should be carried out to remove potential ingress points for feral pigeons. These would include missing rooftiles, broken windows and areas where maintenance work has been carried out and holes left in the fabric of the building.

Roofs should be designed and detailed specifically to exclude birds by keeping all gaps and openings below 20mm

Proofing against bird nesting and roosting

Proofing measures such as netting and stainless-steel spikes can be used to deter birds from roosting on buildings.

Netting mesh sizes for bird proofing will vary according to the species of bird. As a guide, the following mesh sizes are recommended:

Sparrows and similar size birds – 19mm mesh size

Starlings – 28-30mm mesh size

Pigeons – 50mm mesh size

Gulls – 75mm mesh size

Spike systems will deter birds from roosting on ledges that cannot be made inaccessible by netting. They should be fixed in a manner that will ensure that the ledge is adequately covered by the spikes.

Bird proofing is specialist work. An experienced installer should be consulted for advice and proofing strategies.

It should be noted that birds other than those listed on the general licences cannot be prevented from accessing their nest site during the breeding season. To do so would be a breach of the Wildlife (Amended) Act 2000 and prosecution could follow.

Urban pest bird control Pigeons is a complex subject and requires an integrated approach which will include waste management regimes to minimise attractive food sources; maintenance and design of buildings that will reduce potential roosting and nesting sites and proofing strategies that will exclude pest birds from priorities areas.

Pigeons AKA ‘Rats with Wings’

Why do we dread these pests over other animals?

Since the 1930s pigeons have been causing havoc to our cities. From nesting on roofs to defecating buildings. They are commonly known as ‘Rats with Wings’ but do we have reason to despise these birds? Let us take a look

Noise

These pesky birds invade spaces that are not designed for them. They have settled in urban areas and industrial estates and are comfortable making their nest in man made structures. Their short legs and hind toes permit easy perching on pipes and ledges.

Faeces

Not only do they invade our space they also destroy it with their droppings. Their waste is highly acidic and will corrode metal and concrete. Pigeons also carry mites which can cause skin disorders, while dirt from their feathers can exacerbate respiratory problems.

Disease

Most importantly they are a health risk to us. Pigeons and their excretion spread over 60 different diseases. Histoplasmosis, Salmonella and E.coli to name just a few.

Image

A pigeon infestation will promote a bad company image. Seeing a flock of pigeons nesting on the roof of any building or its ledge does not portray a top company image.

Damage

Pigeons nest in drain gutters, blocking them causing damage. They also nest near cables which could lead to a serious fire hazard. Pigeon activity around buildings often leads to structural damage as these resourceful pests can lift roof coverings to make an entry.

How do we control these pesky pests?

In the 20^th century, pigeons were controlled by killing them however nowadays Bird Control Pigeons is much more humane. Controlling them now means preventing them nesting on YOUR building and moving them elsewhere. Our highly trained staff at Central Pest Control can help in moving these birds from your building by putting netting or bird wiring of any shape or size to fit your pest control needs depending on the area invaded.

Did you know? A pigeon dispenses over 10 kg of dung a year!

Pigeon Patrol

Canada’s top wholesaler for bird deterrent products for twelve consecutive years.

Brilliant nature! Help stop rooftop cruelty to our super bright birds.

by Pigeon Patrol | Sep 25, 2024 | 4-S Gel Bird repellent, Animal Deterrent Products, Bird Deterrent Products, Bird Netting

Great news. The petition to reduce the use of bird deterrent spikes on buildings has now almost reached 2000 supporters!

I recently saw a poor Herring Gull dangling dead from a roof top caught by a strip of spiked bird deterrents. I felt I had to do something. That’s why I started the petition.

Share the petition (copy and paste) using the link above with friends or more widely on social media. Add a note asking people to please sign and share the petition themselves. If you’ve already been so kind as to have already shared it please consider sharing again. It may find people at a more convenient time. Thank you.

Birds don’t deserve to die because of these ill placed cruel bird deterrent measures. Help stop the killing of endangered birds such as the Herring Gull and other birds who simply want a place to land and thrive.

City Pigeons

Rooftop birds like crows and gulls are super bright!

Many birds such as corvids (crow family), pigeons, gull and owls are as cognitively capable as monkeys and even apes. Corvids are particularly smart. Its long been known that they can use tools, recognize faces and even leave gifts for people they like. Birds have smaller neurons (signal pathways) than those in mammalian brains, but have many more information-processing neuronal units in their pallium (layers of grey and white matter covering the cerebrum) than the equivalent-sized mammalian cortices.

A recent study (Nieder et al) published in the journal Science involved studying two carrion crows called Ozzie and Glenn. The study showed that crows are capable of thinking about their own thoughts as they work out problems. This level of self-awareness was previously believed to signify higher intelligence that only humans and perhaps a few other mammals possess. It turns out a crow knows what a crow knows, and so it may be the case that they are sentient beings. The bird pallium has neurons that represent what it perceives – a hallmark of consciousness.

In other words the type of higher intelligence crows exhibit is similar to the way humans solve problems. Corvids it turns out, file away relevant knowledge and then explore these filed banks of ‘known information” to arrive at a thought through cation or solution.

3 things you can also do to help:-

Tweet this update or share the petition on social media using the hashtags Nature, birds, NoToBirdSpikes or LetTheBirdsFly

Use a bird image you have taken and post to social media with the petition link asking people to sign and share (use the same hashtags above). Add your own words saying why you think birds should not get hurt or killed by bird deterrents.

Pigeon Patrol

Canada’s top wholesaler for bird deterrent products for twelve consecutive years.

Visual deterrents and physical barriers as non-lethal pigeon

by Pigeon Patrol | Sep 25, 2024 | 4-S Gel Bird repellent, Animal Deterrent Products, Bird Deterrent Products, Bird Netting

A study on a population of pigeons on the University of South Africa’s Muckleneuk campus was conducted over 2 years. Counts were conducted during a baseline year (March 2013–February 2014) to establish the pigeon population index inhabiting the campus buildings, and again in the management year (August 2014–August 2015) once Eagle Eyes™, Fire (Flash) Flags, bird spikes and a combination thereof were implemented on the buildings. An efficacy reduction percentage was determined for each of the control structures. The total pigeon index on the campus declined by 50 % once the control structures were implemented. Control structures; however, differed markedly in efficacy from each other. Whilst bird spikes indicated the highest efficacy at reducing the pigeon population index, seasonality also influenced the efficacy of the control structure. Quantified understanding of the efficacy of pigeon control measures allows urban management to make informed decisions about reducing pigeon populations.

Background

Feral pigeons were first introduced by early Europeans to Southern Africa as a free-flying domesticated species in the seventeenth century (Brooke 1981). However populations both feral (Columba livia Gmelin 1789) and indigenous (speckled pigeon Columba guinea Linnaeus 1758) have since populated urban regions throughout the subcontinent. Urban resources and lifestyles associated with human activity have enabled pigeons to establish populations as a result of the available supply and distribution of food and breeding space (Haag-Wackernagel 1995) resulting in them being considered as the most successful avian coloniser of urban spaces.

Given their long history with humans (Sossinka 1982), it is surprising that pigeons were only first considered to be problematic to the human environment in the 1930s (Sacchi et al. 2002). As pigeon populations increase people start experiencing aesthetic, vital and economic conflicts of interest (Wetherbee et al. 1964) which include the exposure to droppings and debris accumulation (Murton et al. 1972; Fitzwater 1988; Flannery 2009), public health concerns (Hutton 2005; Haag-Wackernagel and Bircher 2009), disturbance (Hutton 2005; Haag-Wackernagel and Geigenfeind 2008), structural deterioration (Hutton 2005; Giunchi et al. 2012) and to a lesser extent, bird strikes (Giunchi et al. 2012). Large flocks of pigeons have been considered to be a nuisance due to their vocalisations (Carle 1959), disturbance from squabs and breeding activities (Hutton 2005), begging (Hutton 2005), potential transmission of pathogens and parasites (Haag-Wackernagel and Moch 2004) and their sheer numbers resulting in an altered enjoyment of private and public spaces (McKeown 2008).

Pigeon control has increased substantially over the decades (Giunchi et al. 2007), with the pigeon control industry booming in the twenty-first century when public views of the birds became increasingly negative and there were calls for the systematic extermination of pigeons in urban environments (Jerolmack 2008). Subsequently, with the increase in pigeon population densities, more pest control strategies have become readily available (Giunchi et al. 2012). These control strategies have been broadly directed at either reducing pigeon numbers through increasing mortality (Haag-Wackernagel 2008; Giunchi et al. 2012), decreasing natality (Giunchi et al. 2007a, b; Haag-Wackernagel 2008; Dobeic et al. 2011) or modifying behaviour through resource management (Haag-Wackernagel 1995; Giunchi et al. 2007a, b; Haag-Wackernagel 2008). Pigeon control is often ad hoc, reactive and unsustainable (Brix et al. 2006), aimed at short-term benefit to enable continued support for pest control businesses (Murton et al. 1972).

Lethal measures have become increasingly controversial and have lost public support (Treves and Noughton-Treves 2005), while non-lethal forms of control are sustainably effective in the long term and are more acceptable to the greater public (Murton et al. 1972; Haag-Wackernagel 1984). This is particularly applicable in light of the recent listing of the feral pigeon as a Category 3 invasive species in South Africa, in terms of the Alien and Invasive Species Regulations, 2014, in terms of the National Environmental Management: Biodiversity Act of 2004 (Act 10 of 2004) of South Africa which permits the legal control of feral pigeons in urban areas (Department of Environmental Affairs 2015; SA 2015: 493).

Non-lethal pigeon control strategies are generally directed at the pigeons’ visual, auditory and tactile senses; however, habitat modification and reduction can also be achieved by physical barriers. According to Jacobs (1992), pigeons are able to see in colour and ultra-violet spectrums to aid foraging, signalling and sex recognition, and thus visual control strategies aimed at irritating or impersonating danger have varying colour spectrums. These include decoys (Harris and Davies 1998), moving lights and objects, lasers (Blackwell et al. 2002), threatening images and reflective items. Hutton and Dobson (1993) and Hutton (2005) have both found that visual deterrents have their limitations and are generally ineffective due to habituation by the pigeons.

Habitat modification through the placement of physical barriers preventing pigeons from perching on buildings and other urban structures are used widely due to their durability and acceptance by the public (Giunchi et al. 2012). Haag-Wackernagel and Geigenfeind (2008) suggest that through the restriction of entrance dimensions and the exaggeration of sloping surfaces, access prevention to ideal roosting and nesting sites can be achieved. Anti-perching devices such as sprung wires (Hutton 2005) and bird spikes (Seamans et al. 2007), or the total exclusion through netting (Hutton and Dobson 1993) can be used to deter pigeons from making use of buildings in urban environments. Cost may be a limiting factor in their implementation, and the effectiveness of these barriers can depreciate over time if these devices are not maintained (Hutton 2005).

Nevertheless, every structure and strategy has its advantages and disadvantages (Hutton and Dobson 1993). However, regardless of the control method used, if the benefits of the resources for the pigeons outweigh the costs of enduring device-related discomfort, pigeons will override any system (Haag-Wackernagel and Geigenfeind 2008). Research suggests that science seems to be lacking in quantitative reviews of various control methods and their effectiveness at reducing pigeon populations (Buijs and Van Wijnen 2001; Fukuda et al. 2008). The level of pigeon reduction of such devices needs to be quantified so that urban management can make informed decisions about the cost effectiveness and efficacy at reducing pigeon populations with regard to non-lethal control methods.

The University of South Africa’s (Unisa) Muckleneuk campus in Pretoria is host to a large number of pigeons. The birds gain access into the buildings through open access points such as loose exterior ceiling boards and open electrical and air conditioning ducts (cabling ducts) positioned on the exterior of the buildings. This easy access increases the number of protected and sheltered breeding and roosting sites available. It has also increased health concerns relating to the build-up of their faeces and associated fungi, nest mites and bird lice which have been reported to infest the offices and affect the staff working in certain buildings on campus. Faeces and accumulated nesting material build-up on the various external structures of the campus buildings have become an issue of concern. According to Ntshoe (pers. comm. 2013), large financial investments have been made in order to manage the birds and their associated problems on an ad hoc and reactive basis.

This paper evaluates non-lethal humane pigeon control strategies with particular focus on visual deterrents and physical barriers on the Unisa Muckleneuk campus and will examine the following objectives and null hypothesis.

Objectives

To determine if the control structures have decreased the pigeon population index on campus.

To determine if pigeons will move from a building with control structures to an untreated building.

To establish if seasonality influences the efficacy of control structures.

To validate the industry percentage reduction claims with regard to control structures.

To evaluate the efficacy percentage reduction of Eagle Eyes™, Fire Flags, bird spikes and a combination thereof on the pigeon population index.

Null hypothesis

Control structures, namely Eagle Eyes™, Fire Flags, bird spikes and combinations of these, will not significantly differ from each other in efficacy at reducing the pigeon population index.

Study area

Unisa (−25.76776, 28.199158) is situated on top of a hill (1411.19 m above sea level) near the central business district of Pretoria in Gauteng in South Africa. The city is surrounded by the Magaliesburg mountain range in the transitional zone between the Central Bushveld and Moist Highveld Grassland vegetation types (Kruger 2004). The city has a moderate, warm temperate climate with an annual minimum and maximum temperature average of 13 °C (June) and 24 °C (January) respectively which was measured during the course of the study. According to the South African Weather Service (2010), precipitation averages 677 mm, while relative humidity ranges between 44 and 75 % annually. Pretoria experiences 3 254 h of sunshine a year with an average of 2.4–2.7 days of cloud cover recorded annually (South African Weather Service 2010). The Pretoria region within a 20 km radius of Unisa includes commercial, industrial, suburban and rural areas, with farming and crop (maize, soya, sorghum and sunflowers) production in the surrounding districts (Collett 2015).

The campus is located within a green belt which includes the surrounding Groenkloof Nature Reserve, Fountains Valley, Apies River, Voortrekker Monument and Freedom Park. Various small mammals and bird species inhabit the university’s grounds. These include avian migrants and small raptors.

Established in 1972, the Muckleneuk campus consists of seven administrative and academic buildings; however, for the purpose of this study only the following five of the seven buildings were investigated as part of the pigeon research: Theo van Wijk building, OR Tambo building, AJH van der Walt building, Cas van Vuuren building and Samuel Pauw building (Fig. 1). Each building is unique in its design, providing various roosting and nesting site possibilities for the pigeon population index on the campus. Academic and administrative offices are positioned lengthwise along the buildings and face out onto balconies.

Theo van Wijk, the largest building positioned on the far western side of the campus, has 11 levels uniform in design with balconies and exterior cabling ducts running the length of the building. Due to its y-shape, the building offers two north facing and two south facing aspects. The Philadelphia cafeteria is positioned on the third floor, which includes an extensive catering balcony.

The AJH van der Walt building is positioned on the northern side of the campus facing an undeveloped vegetated mound which meets the campus’ northern boundary. All seven levels are continuous in balcony and cabling ducts design.

To the east of the campus is the library, housed in the Samuel Pauw building, roughly hexagonal in shape with eight levels and continual balconies. Beyond this building towards the campus boundary in the east is parking space and natural vegetation.

OR Tambo, the administrative building, is positioned to the south. It is the tallest building on campus with 14 levels. Balconies and cabling ducts provide uniform exterior structural design, with the exception of the Good Hope cafeteria and balcony positioned on level four.

Adjacent to the OR Tambo building is the Cas van Vuuren building with seven levels and no exterior cabling ducts positioned above its balconies. Natural areas extend to the southern and south-western boundaries.

A characteristic of all the buildings are the loose, broken or open exterior ceiling boards and cabling ducts which provide additional roosting and breeding space for the pigeon population index on campus.

Methods

This study took place over two years. During the first year data was collected for a full year from the beginning of March 2013 to the end of February 2014 to provide a baseline year to determine the index of the pigeon population inhabiting the buildings on the Muckleneuk campus. This data was used to determine the efficacy of the control measures implemented on the campus buildings during the second year (August 2014–August 2015).

For each year adult and juvenile pigeons were counted during the pigeons’ bimodal foraging activity periods, which have been recorded to peak in the morning and afternoon (Rose et al. 2006; Soldatini et al. 2006). These counts took place early morning during the first 2 h after sunrise and again in the evening during the last 2 h before sunset, once a week for 52 weeks. If the particular chosen day for counting experienced extreme weather conditions, then the next consecutive day with fine weather was chosen and documented.

The observer maintained a standard designated route in a west to east direction, counting each of the campus’ five buildings during the course of the research period. Observations were aided binoculars, digital camera and dictaphone, later transcribed onto data sheets. Double counts of individuals taking off and perching on the same building was taken into consideration and avoided. As the pigeons were wild and free roaming, the exact number of pigeons on campus could not be determined. An increase or decrease in the number of pigeons counted was in essence a reflection of the unknown population size and directly correlated to an increase or decrease in pigeon presence on campus (Gregory et al. 2005). Presence was represented as an index to monitor the extent of the increases or decreases as actual numbers could not be attained through the methodology implemented. As the index reflects a portion of the pigeon population, a portion which may be change over time, methodology was therefore standardised to mitigate variability (Johnson 2008). The paper will therefore refer to indices to convey the extent of the pigeon presence, and its changes over time. The results of the baseline year were therefore interpreted as an index of pigeon population size. The use of the term ‘population’ in this study does not refer to a biological population as a demographic unit but rather as a population index indicative of the census technique employed.

During the second year, once the baseline year was completed, various pigeon control structures were installed on four buildings (Theo van Wijk building, OR Tambo building, Cas van Vuuren building and Samuel Pauw building) for the management year (August 2014–August 2015, 52 weeks). One of the buildings, AJH van der Walt building, was used as a control building without any pigeon control structures or strategies to determine whether pigeons deterred from surrounding buildings with control structures simply moved to an untreated building as suggested by Mooallem (2006).

Pigeon control structures chosen for this study included Eagle Eyes™ (visual deterrent) which are rotating prisms that reflect light within the ultra violet spectrum designed to interfere with the pigeons’ line of flight as the light causes a distraction (Eagle Eye 2015) (Fig. 2); Fire (Flash) Flags (visual deterrent), made from reflective gold and silver plastic, are designed to move with the wind to give the impression of fire and danger (Eagle Eye 2015) (Fig. 3); bird spikes (physical barrier), which are dual-pronged, stainless steel spikes continuously placed along the ledge of a building aimed at preventing pigeons from perching (Fig. 4); and the combination of the above mentioned control structures (Eagle Eyes™, Fire Flags and bird spikes) recommended by a well-known pest control company in South Africa for optimal pigeon deterrence.

The pest control company marketing and selling the pigeon control structures identified the optimal placement of each control structure tested in this study per building on campus to ensure that each building was suitably covered by the chosen structure for pigeon control purposes.

The largest building, Theo van Wijk building, is positioned on the far western side of the campus. Due to its extensive size and y-shape creating two north and two south facing aspects, Eagle Eye™ units were chosen. Sunlight reflected by the 36 units was able to cover a greater surface area relative to the other control structures, and its proximity to other buildings contributed to the control structure choice as light from the units would affect surrounding buildings thus influencing their respective control strategies. Units were placed on each balcony of the 11 stories and at regular intervals along the roof (north and south facing).

OR Tambo, the tallest building with 14 levels, was selected to test the Fire Flags due to the updraft of wind that is experienced at such high altitudes. Eighty units were placed along the levels (north and south facing).

The Cas van Vuuren building was identified for use of bird spikes as the building does not have the exterior electrical and air conditioning ducts (cabling ducts) which are positioned just below the balcony ceilings above the office windows of other buildings on campus. These ducts provide ideal sites for pigeons to roost and nest on. A single continuous strand of bird spikes (1720 m) was positioned along the length of the balcony ledge on all seven levels (north and south facing).

The university’s library, Samuel Pauw, hexagonal in shape, was chosen for the implementation of the control structure combination recommended by the pest control company. This included six Eagle eye™ units, 12 Fire Flag units and 2790 m of bird spikes applied to the eight levels of the building.

The same methodology used in year one was applied in the second year to determine the efficacy of the control structures on the pigeon population index. Arithmetic means and standard errors of the monthly pigeon population indices are depicted graphically over the course of the two years. Pigeon population index and efficacy rate was determined by calculating the percentage change in the number of counts of pigeons between the baseline year and management year in which the control structures were implemented. This indicated the reduction in percentage of each control structure on the pigeon population index.

To test whether or not there was a difference in the mean efficacy percentages between the different control structures a one-way ANOVA was used. Where significant differences between the control structures were observed, Bonferroni post hoc tests were employed to determine which of the control structures differed significantly from each other in one-to-one comparisons.

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Bird Deterrent Solutions for Crop Protection:

by Pigeon Patrol | Sep 25, 2024 | Animal Deterrent Products, Bird Deterrent Products, Bird Law

Weeds, pathogens, and animal pests are among the pests that pose a threat to the productivity of crops meant for human consumption. Bird-caused crop losses pose a serious and costly challenge for farmers. This work presents a survey on bird deterrent solutions for crop protection. It first introduces the related concepts. Then, it provides an extensive review and categorization of existing methods, techniques, and related studies. Further, their strengths and limitations are discussed. Based on this review, current gaps are identified, and strategies for future research are proposed.

Keywords:

birds; deterrents; agriculture; crops; survey

1. Introduction

Pests, especially weeds, pathogens, and animal pests, pose a threat to the productivity of human-consumable crops. Bird-caused losses to fruit crops pose significant and expensive problems for farmers. Estimates on potential and actual losses caused by different bird species were discussed in a study carried out in Sweden between 2000 and 2015 [1]. During those years, there were 2194 complaints of crop damage, corresponding to a total loss of approximately 34,500 tons of various crops. The bird species that caused the most damage were, in order of the percentage of total losses from highest to lowest, the common crane (Grus grus) (33.7%), the barnacle goose (Branta leucopsis) (33.5%), the greylag goose (Anser anser) (26.6%), the bean goose (Anser fabalis fabalis) (2.6%), and the whooper swan (Cygnus cygnus) (2.2%). The remaining 1.4% of the total losses were caused by other birds.

Another study [2] aimed at finding out which bird species were directly related to crop damage. Visual damage was collected on 60 randomly selected plants: 12 at each cardinal point and 12 inland in New York State. It was focused on four different crops from 81 field locations: sweet cherry—23; blueberry—12; apple—24; and vine—22. Damages were estimated at 2.3% for apple fields, 3.6% for grapes, 22% for blueberries, and 26.8% for sweet cherries. In addition, surveys were also conducted on farmers with those crops via the Internet, mail, and telephone in New York, Michigan, Washington, Oregon, and California. New York farmers alone pointed out that, all together, they lose about $6.6 million per year and that 65.6% of them are taking measures to scare the birds away. Half of the farmers confirmed that birds are the biggest factor in crop loss.

A study conducted in Poland [3] concluded that, in the years 1974 and 1980, 22% and 16%, respectively, of cherry crops were destroyed by sturnids (Sturnidae). The same study also conducted another survey in four districts of Poland aimed at all crops. In Gdansk, 471 surveys were filled out, of which 27% stated with certainty that their fields were damaged by rooks (Corvus frugilegus), and 59% had suspicions that the damage that appeared on their crops was also caused by rooks. In Warsaw, 51% of 378 questionnaire respondents were certain that they had damage caused by rooks. In Kielee, 56% of 351 questionnaire respondents reported damage, and, in Wroclaw, 58% of 276 questionnaire respondents also confirmed damage caused by rooks. In that same survey, overall bird damage was also collected for four crops: wheat, oats, corn, and barley. In the four districts, corn losses ranged from 22% to 32%, wheat losses from 10% to 13%, barley losses from 3 to 18%, and oat losses from 8 to 15%.

These results highlight the importance of applying bird deterrent techniques to minimize crop loss due to bird damage. These techniques can be classified into six major groups. Visual techniques activate a trigger in the bird through a visual stimulus. Auditory techniques activate a trigger in the bird through an auditory stimulus. Chemical methods use chemical agents to cause discomfort or to kill the birds. Exclusion methods consist of simply creating a physical barrier so that the birds cannot get to a certain area. Habitat modification is when the farmer changes the factors that birds like about that environment so that it is pleasant for them to look elsewhere. Removal methods consist of forcibly removing birds from a certain environment, either by trapping or killing them.

Although many deterrent techniques based on these concepts have been tested with success, there is a lack of a systemic approach to bird management. This work aims to study and discuss challenges and opportunities for improvements in the methods and techniques that have been used as bird deterrents for crop protection. It is organized as follows: Section 2, Section 3, Section 4, Section 5, Section 6, Section 7 and Section 8 describe the different methods and techniques used as bird deterrent solutions. Section 9 highlights the gaps and identifies trends for future research in the area. Finally, Section 10 presents the conclusions.

2. Visual Deterrents

Visual deterrents present a visual stimulus to the birds that can trigger fear or curiosity. The dangerous feeling can be triggered by a real or simulated predator. In the case of real predators, this can lead to birds’ deaths. By contrast, there can be the use of something birds are not familiar with, such as scarecrows, dyes, lights, reflecting tape, optical gel, kites, balloons, or others. Some of these visual repellents can incorporate audio deterrents as well.

2.1. Scarecrows

Scarecrows, shown in Figure 1a, are the oldest bird deterrent approach [4,5]. Most scarecrows are human-like effigies usually made from inexpensive materials like grain sacks or old clothes filled with straw. The more realistic the facial and body shape, the more effective scarecrows are likely to be. They can be more detectable if they are painted in bright colors [6]. Commercially made scarecrows are also available to purchase, such as the Scarey Man mannequin [7,8]. It is a 5′6 inflatable scarecrow operated via a 12 V battery with an autonomy of 14 days, which inflates intermittently for 25 s every 18 min. It can be equipped with an LED light to illuminate the interior of the scarecrow and a speaker to emit sounds. This can be operated separately from the pump used to inflate it.

Figure 1. Visual deterrents: (a) scarecrows; (b) reflecting tape; (c) hawk balloons; (d) aircraft; (e) RC aircraft; (f) lights.

By imitating the form of a predator—human or other bird—the scarecrows cause the bird to awaken the instinct to fly to escape from a predator. The more real the scarecrow is visually, aurally, and in actions (i.e., movement), the more effective it will be.

Scarecrow-type devices are considered ineffective when used alone or effective only when used for a short period of time, because birds can get used to visual stimuli [9,10,11,12,13,14]. In [5,15,16], it was concluded that the effectiveness is improved if they are relocated every 2 to 3 days. Scarecrows that move and are used in conjunction with other devices are much more effective than those that stand still and are used alone. In [17], a mannequin was used to scare oriental turtledoves (Streptopelia orientalis). It proved to be more effective than tests performed with homemade scarecrows or kites. More recently, some scarecrows with pop-up systems have begun to appear. Nomsen [18] reported that a human-shaped mannequin activated with a dual propane cannon system was quite successful at scaring off blackbirds (Turdus merula) within four to six acres in a sunflower field. Ducks and geese were also found to be more easily frightened than blackbirds by this system. Naggiar [19] concluded that some bird scarecrows are completely ineffective, whether static or mobile, in an experiment done on waders (Charadriiformes). After only two hours, the birds were already habituated.

2.2. Reflectors and Reflecting Tape

Reflective tape, shown in Figure 1b, is a rubber band composed of three layers: one side is a sheet of silver metal, and the other side is colored with a synthetic resin [20]. This tape emits flashes of light when the light hits it and produces some sounds when the wind hits it. Because of the noise and reflection, this type of tape is often found in agricultural implementations.

This device does not directly arouse any instinct in birds. Initially, they will avoid staying in the space where the tapes are applied due to their instinct to avoid unfamiliar things. They also show some startling at the reflected lights and noises produced. Because there is no strong biological connection, it is highly likely that they will quickly get used to the presence of reflective tape.

There have been several studies regarding the use of reflective tape at airports and on plantations. More recent studies focus on reflective tapes rather than just bright, eye-catching objects. Reflective tapes produce noise when they snap in the wind, and it is believed that this auditory stimulus makes reflective tapes more effective than other reflectors. Bruggers [20] used reflective tape (0.025 mm thick and 11 mm wide) to deter birds from crops, sunflowers, and sorghum crop fields. The tape was successful at scaring birds away when suspended above ripening crops in parallel lines and when crop entrances were protected as well. The strong winds may also have helped to improve the effectiveness of the device by making more noise. Dolbeer [21] used reflective tapes to repel blackbirds from crops by tying the tapes to a rope three, five, and seven meters apart that was attached to poles three meters apart, with the tapes at a height of 0.5 to 1 m at the lowest point between the poles. The three-meter spacing proved to be more effective at scaring away the birds than the five- and seven-meter spacings. However, this technique is not valid for all bird species and was no longer effective when the reflective side was not seen (due to coiling).

Summers and Hillman [22] tested a 20 mm thick red fluorescent tape to scare geese off winter wheat fields in the United Kingdom. Half of a 20.2-hectare field was used as a control, while the other half was fitted with reflective tape. Another control field with an area of 7.5 hectares was equipped with a gas cannon and two scarecrows in the field. The lines were tied at 40 to 60 m between the rows of wheat. It was concluded from this study that the tapes were more effective at scaring away geese and that the field with the reflective tape lost only 1% of its production to the birds, compared to the 6% lost to the control fields. It was also concluded that the geese grazed two meters away from the application area.

2.3. Hawk Kites and Balloons

Kites and balloons, shown in Figure 1c, are the mobile versions of predator models. These devices are tied to the ground or poles, so they do not run away from the site. They are supposed to arouse the bird’s instinct of fear, because they are flying in an area that is supposed to be controlled by a hawk. As it is not a real threat, the birds will eventually get used to the presence of these devices [23].

2.4. Dead Bird Models

Dead bird models can be a replica, or an actual dead bird set in the ground to make it seem like the bird has fallen and died there. Bird bodies have been used as repellents in both agricultural [24] and airport situations [15,25,26].

Gull replicas are used in an intensive gull control program that occurs annually at a large gull colony at Toronto’s Leslie Street Spit [27,28,29,30]. The gull replicas consisted of a plastic bottle with two gull wings tied on it. They are tossed in the air to simulate injured seagulls. This technique, used along with falconry and pyrotechnics, successfully prevented seagulls from nesting in large parts of that area. Some airports kill seagulls and then fling them into the air when using pyrotechnics. Dead bird models will deter some birds, but their effectiveness is limited to the habituation period.

2.5. Aircraft

Both planes and helicopters, shown in Figure 1d, have been used to chase and scare away birds on farms. But this method is not recommended at all, due to compromising the safety of the aircraft crew. Hence, there is the need to scare birds away from airports [23].

2.6. Radio-Controlled Aircraft or Unmanned Aerial Vehicle

Drones, or Unmanned Aerial Vehicles (UAVs), shown in Figure 1e, can be used to threaten and scare birds. The aircraft can be painted in predator-like colors or have the shape of a hawk.

Radio-controlled (RC) aircraft may scare birds off both farms and airports [15,31,32,33]. However, RC aircraft require a skilled operator [6], and, for this reason, it has not been widely implemented at airports [34].

One experiment with a hawk-shaped aircraft proved to be remarkably effective at scaring away starlings (Sturnidae) and plovers (Charadriinae) at the Vancouver International Airport, as well as ducks (Anas platyrhynchos) and geese (Anser anser) on Western Island, Vancouver, B.C. [32,35]. Some birds demonstrated escape techniques from the aircraft as if it was a real hawk. However, this aircraft has proven to be difficult to fly and, therefore, requires a specifically trained operator. A more conventionally shaped aircraft can be painted in the colors of a predator [31].

Another approach is to use UAVs as bird repellent. Due to their versatility, UAVs can be beneficial in solving this problem without requiring a human pilot. However, due to their low battery capacity, which equals low flight duration, it is necessary to evolve path planning optimization, as described in [36].

2.7. Lights

Flashing, rotating lights, and spotlights, shown in Figure 1f, can be used to scare birds away [37]. The reason why lights scare birds away is not truly clear. It is thought that it is because birds have not yet learned them. Thus, they are a novelty that causes them anxiety, and they prefer to fly away. At night, it is believed that lights dazzle and disorientate the birds. Lights are also used to warn birds of dangers, such as those implemented in aircraft.

Spotlights have been used to scare ducks away from landing and grazing in grain fields. Some nocturnal migrants have been found to take evasive maneuvers when spotlights were pointed at them [25]. There is a catch, however, in that overcast or foggy nights can attract birds.

Most of the information about how effective flashing lights are in addressing bird-related hazards comes from airport and aircraft applications. More recent studies show mixed results regarding their success. Lawrence [38] reviewed various pieces of evidence and concluded that flashing lights scare away birds.

The study [38] showed that, during the day, aircraft landing with the landing lights on suffered fewer bird strikes than with the lights off. The simultaneous use of flashing anti-collision lights brought the numbers down further. These lights have more effect on lapwings (Vanellinae) than on gulls (Larinae). However, Zur [39] found no difference in DC-9 aircraft with landing lights on versus those with them off.

Briot [40] observed the reactions in crows (Corvus Corax), magpies (Pica), and jays (Cyanocitta cristata) that were on the ground when two aircrafts passed at low altitudes. One had no lights, while the other had 100.000 white lights flashing at a frequency of 4 Hz. The distance between the aircraft and the birds was observed. It was concluded that there was not a significant difference between the altitude at which the aircraft passed and whether it had the lights on or not. A small difference was noticed when increasing the frequency at which the lights flashed. The procedure of the experiment eventually was not the most appropriate, as it is believed that the birds were frightened more by the approaching aircraft than by the lights themselves.

A study was conducted to test the effectiveness of lights on laughing gulls (Leucophaeus atricilla) and American kestrels (Falco sparverius) [41]. It was observed that lights flashing at 50 Hz caused the birds’ heart rates to increase more than those at 5, 9, or 15 Hz. However, in the tests during longer periods of time, the average heart rate was higher at lower frequencies than at higher frequencies. Laty [42] suggests that the frequency of lights should not exceed 100 Hz. Studies have been carried out with frequencies of 8–12 Hz in gulls (Larinae), sturnids (Sturnidae), and pigeons (Columba livia) [43,44]. Belton [43] and Solman [44] recorded that gulls took, on average, 30–45 min longer to land on the site where they were to eat with a 2 Hz magenta flashing light than the untreated site. No improvement was recorded when the light frequency was above 60 Hz.

Tests carried out on laughing gulls (Leucophaeus atricilla) and American kestrels (Falco sparverius) by Green et al. [45] concluded that the birds’ heart rates did increase, and they did become attentive to the light, but it did not necessarily mean that it frightened them away, as they did not show that behavior, at least when using only the lights without any other method of deterring the birds. If this equipment is used in conjunction with another preferably containing movement, it may awaken the avoidance effect in the birds. They also recommended the use of several types of colors and frequencies in lights.

The use of flashing lights at an oil spill had a 50–60% success rate at scaring birds away [15,46]. Some tests have shown positive results in scaring away waterfowl (Anseriformes), waders (Charadriiformes), sparrows (Passer), gulls (Larinae), and other species [15]. Other tests have been ineffective against waterfowl (Anseriformes) [13], gulls (Larinae), blackbirds (Turdus merula), and starlings (Sturnidae) [15].

2.8. Summary

A summary of the studies that have considered visual deterrents is provided in Table 1.

Table 1. Summary of the studies using visual deterrents.

3. Auditory Deterrents

These are methods that use auditory techniques to deter birds. Most auditory deterrents also have a visual component.

3.1. Shotguns and Rifles

Weapons such as shotguns, shown in Figure 2a, when fired with real ammunition, produce a loud noise that can scatter the birds. Moreover, the shot fired can also hit the bird and kill it at fisheries operations [47,48,49,50], in agricultural fields [18], and at airports [15,34]. Even though birds can be driven away, they get used to the sound of the shots. So, it works only temporarily, and there are records of birds that returned to the site shortly after being dispersed by such noises [51,52].

Figure 2. Auditory deterrents: (a) shotgun ammunition; (b) pyrotechnics; (c) gas cannon; (d) AV-alarm; (e) predator sounds, high sounds, ultrasound, and infrasound.

3.2. Pyrotechnics

Pyrotechnics, shown in Figure 2b, consist of the use of rockets or small explosives, which emit very loud sounds and flashes of light. The resulting shockwave itself also contributes to dispersing the birds.

The similarity in sound to shotguns makes birds that are regularly hunted to have an aversion to these sounds, which contributes to their dispersal. A rope firecracker is a method that uses small explosives attached to a rope. This rope is set on fire at one end, thus varying the explosion time between devices. It is considered an unsafe method.

Pyrotechnics only have the intended effect temporarily, because the birds will get used to the noise [23].

Flares

Flares are alternatives to fireworks, which can be fired from an adapted gun or placed at a specific point and ignited. When used, they emit a kind of flame and smoke that may deter birds [25]. It is not as effective as shooting ammunition or using pyrotechnics, since it does not produce much noise.

Pistols

Pistols can be used just like shotguns or rifles. They are alternatives with less range for smaller areas. In addition to ballistic ammunition, they can also fire flares, as described above, and ammunition that produces a kind of crackle and/or a loud whistle [53,54,55]. Pistols are a widely used alternative, because they are easier to use than pyrotechnics, safer than real shotgun ammunition, and have lower associated costs.

As with most auditory deterrents, if they are not changed frequently, birds get used to the noise they produce and they lose the intended effect.

This method is used in places such as airports, and, in the long term, it has an effect in the presence of birds. Aguilera [56] registered some results where the presence of birds decreased by about 88%, but only for a week.

Mortars

The mortars are launched from the ground. While the launched device is in the air, it produces a hissing sound until it explodes [25]. While conventional pyrotechnics such as firecrackers are only useful at night, mortars are also useful during the day. Moreover, the noise they produce is much louder than fireworks.

The disadvantage is that it requires a qualified person to be able to handle these devices. It is also an unsafe option, since it is based on explosive devices.

3.3. Gas Cannons

Gas cannons, shown in Figure 2c, are devices that produce a kind of explosion by igniting a gas, usually propane or acetylene. This sound is intended to resemble a gunshot [57,58]. These cannons work through timers or by remote control [54,55]. To increase effectiveness, some have variable time intervals and automatically rotate.

These cannons only show positive results if they are moved after a few uses so as not to create habituation in the birds. It is also possible to improve the results with this method by combining it with other dispersal methods [59,60,61].

As with other auditory methods, this approach only works in the short term, because the birds get used to the sound. It is also necessary to position the cannons in strategic locations so that the leaves on the trees and other types of obstacles do not affect the sound and its effectiveness. Cannons cannot be used in certain places, because they present a high risk of fire.

3.4. AV-Alarm

The AV-alarm, shown in Figure 2d, is a device that produces sounds in the range of 1500 to 5000 Hz. These devices are controlled by timers and can be powered by photovoltaic panels or batteries.

The sound emitted by the AV-alarm is synthetic. Thus, there is no biological basis that links the sounds to the instinct to flee. It is believed that the positive results are due to the loud sounds emitted and because birds have never heard them. The AV-alarm has been used mostly in agricultural fields to scare birds away from crops.

Th AV-alarm is successful at scaring birds away from small crops [15,25]. It has also been shown to be effective in reducing the damage to grapes caused by European starlings (Sturnus vulgaris), cape sparrows (Passer melanurus), and masked weavers (Ploceus velatus) [62].

The AV-alarm has demonstrated its ability to scare birds away, but is thought to work best in conjunction with other techniques. For example, this device could scare away starlings (Sturnidae) from blueberries crops, but, in conjunction with shotguns or propane cannons, it worked better [63]. Potvin et al. [64] found that combining an AV-alarm with gas cannons provided better results at scaring landbirds (Telluraves) off cornfields in Quebec than when used separately.

There are also negative results from the AV-alarm [65]. It was reported that the device is not as effective as distress calls in repelling birds. Bomford and O’Brien [66] and Devenport [67] also noted that birds become accustomed to these sounds. Thompson et al. [68] concluded that the heart rate of starlings had an insignificant change when exposed to the sounds of the AV-alarm, when compared to the heart rate when listening to distress and alarm calls. Crummet [69,70] also conducted a study to find out how effective the AV-Alarm would be in dispersing birds that were used to the water environment from watery terrain. However, it didn’t provide enough data to allow an assertive conclusion about its effectiveness.

3.5. Predator Sounds

Predator sounds, shown in Figure 2e, can be recorded, and played back to disperse birds, as they will associate them with predators, and the natural reaction will be to fly away. These sounds could be from humans or predator birds [71,72].

However, the sounds may have the opposite intended effect, because, instead of flying away, some birds can try to attack the predator to protect their young, thereby attracting even more birds.

3.6. High-Intensity Sounds

High-intensity sounds, shown in Figure 2e, can result in discomfort to the bird. It aims to cause nervousness and startle the birds, thereby causing them to disperse.

Some of these sounds can be made with air raid sirens. In [73], these sirens were tested, and very positive results in clearing an area were observed. However, this effect only lasted for a few days.

3.7. Ultrasounds

Ultrasounds, shown in Figure 2e, are above the range of sounds that human beings can hear (i.e., from 20 Hz to 20,000 Hz). Some birds can pick up sounds above 20,000 Hz, although they do not communicate at such high frequencies. Nevertheless, no reaction has been shown from birds to this sound frequency [74]. Beuter and Weiss [74] found evidence that gulls (Larinae) can hear this sound frequency. It has been observed that the number of birds present in the areas where this method has been used only decreased by 5% or less [75].

3.8. Infrasounds

Some recent studies claim that infrasounds, shown in Figure 2e, may disperse birds. Just as with ultrasounds, the birds would have to be able to pick up these sounds and associate them with danger [76]. Although there are no concrete results about this method yet, it is believed that, as with all other auditory deterrents, they create habituation in birds after a brief period.

3.9. Summary

A summary of the studies that have considered auditory deterrents is provided in Table 2.

Table 2. Summary of the studies using auditory deterrents.

4. Chemical Deterrents

Chemical aversion techniques have been used in a variety of contexts, from residential areas [77,78] and cities, to agriculture and airports [79,80,81]. Birds do not tend to get used to these types of techniques.

4.1. Tactile Repellents

Tactile-type repellents, shown in Figure 3a, are sticky substances that are used to prevent birds from staying in certain places, such as corners of buildings, antennas, statues in cities, lights, and signs at airports. They can be found in various forms of application, such as tubes, spray cans, or caulking guns. Natural plant-based substances have also been tested [82].

Figure 3. Chemical deterrents: (a) spikes adhesive; (b) Avitrol; (c) ReJeX-iT.

This type of technique does not trap birds but scares them away by the sticky feeling they get on their feet. However, it is not clear why birds avoid these substances [23]. When plant-based substances were used, agitation and hyperactivity were detected in the birds [23]. It is suspected that this comes from a reaction between the plant compounds and the skin on the feet.

No studies have been found that prove the effectiveness of these repellents. Clark [82] reported that starlings (Sturnidae) became agitated and hyperactive after having their feet in contact with a substance using a 5% concentration of oil extracted from cumin, rosemary, and thyme. The result of this experiment suggests that it is possible to use non-lethal, plant-based chemical methods.

There are also mechanical methods that prevent birds from landing in certain places by using sharp objects such as barbed wire or nails. Some commercial versions are available such as “Nixalite” [23].

4.2. Behavioural Repellents

Disorienting substances such as Avitrol [23], shown in Figure 3b, and Methiocarb [23] are poisons that, in non-lethal doses, can cause disorientation and erratic behavior. These poisons are added to bait, and, usually, only a small portion of it is treated so that only a small number of birds in a flock are affected.

The goal is to cause a chain effect whereby when one of the birds becomes startled and flees, the whole flock follows it [15,83,84]. The warning signal can be given to the other birds 15 min before the poison starts to be digested, and the effects can last up to 30 min after digestion. If the dose is too high, it can lead to the bird’s death. Tremors and convulsions have been reported in birds before they die; this can cause the flock to leave the site. Unaffected birds from the flock eventually escape due to the warning signal from the flock mate.

These agents have been tested on starlings (Sturnidae), blackbirds (Turdus merula), and passerines (Passeriformes) [15,83,84,85,86]. The United States Air Force has tested this poison on seven air bases and concluded that it is effective in deterring these birds and a few others, such as crows (Corvus Corax) [87].

Even though Avitrol is highly effective, it is very difficult to dose it correctly to cause the desired effects without killing the birds. Birds may even die later, which can cause other social issues.

Another problem that has been noted is that birds avoid certain baits that they have experienced before. Gulls (Larinae) have been reported to notice this quickly. They stop eating what has been used as a bait. The problem with this is that there is a very limited number of baits that can be used, and each bait carries a different dose of Avitrol (i.e., the dose for a certain amount of bread is not the same for the same number of cornflakes).

4.3. Methyl Anthranilate—ReJeX-iT

ReJeX-iT, shown in Figure 3c, is the name for a brand that sells a bird repellent based on a natural substance found in some plants, called methyl anthranilate. For example, concord is a variety of grapes that many birds avoid eating because they contain methyl anthranilate.

This repellent works as a non-toxic substance to birds, which do not like its taste. It can be found in both liquid and powder and can be mixed in both food and water. It can also be sprayed in the air. Ortho-aminoacetophenone, which is also non-toxic, shows positive results in repelling or dispersing birds [88].

In [23], several tests were conducted with this product. They were performed in the laboratory on several bird species feeding on fruits, grains, truffles, and in water. It was concluded that ReJeX-iT can be effective if used in a high concentration. In some experiments, the applied dose of ReJeX-iT was insufficient and did not lead to the intended effect.

Methyl and dimethyl anthranilate have an unpleasant taste to birds. In [89], experiments were conducted with ducks and geese. They were given treated and untreated seeds. When only treated seeds were offered, both geese and ducks significantly reduced the amount they ate daily. The ducks showed a slightly higher tolerance compared to the geese. The experiments lasted from 2 to 4 days. The birds only increased the daily food dose due to hunger.

Methyl anthranilate was also used in a test conducted by Belant et al. [90] where it successfully repelled some bird species from water puddles in the field. However, another test conducted by Belant et al. [91] showed that the concentration used in the previous test was not effective for Canada goose (Branta canadensis). Belant et al. also concluded that geese did not learn from the previous contacts with the substance.

Problems with the application of ReJeX-iT prevented the testing of its effectiveness for repelling pond birds in [92]. But the results were promising, as the number of birds was reduced after treating the ponds with this repellent.

4.4. Summary

A summary of the studies that have considered chemical deterrents is provided in Table 3.

Table 3. Summary of the studies using chemical deterrents.

5. Exclusion Deterrents

These are devices or materials used to serve as a physical barrier. If access to a certain area, for example, where there is food or shelter, is restricted, the birds will leave the area and move on. There are also apparent barriers (i.e., there is no actual barrier).

Physical barriers are normally made up of wire mesh, polyethylene, or other synthetic materials and serve to prevent birds from approaching a specific area. They also serve to prevent them from nesting in these areas. The metal mesh can also be interconnected with electrified wires so that when birds land there they receive a harmless shock [93,94,95].

5.1. Overhead Netting

Overhead nets, shown in Figure 4a, are made up of several lines or wires interwoven. Nets may have smaller or larger meshes according to the bird species and are placed over a specific area. Birds can be deterred by the nets, even if the mesh spacing is sufficient for them to pass through. It is thought that birds are deterred by the fact that the mesh lines or wires are difficult to see.

Figure 4. Exclusion deterrents: (a) overhead net; (b) bird balls.

This method was initially recommended to prevent waterbirds (Aequornithes) from accessing aquaculture ponds [96]. Later, it was used to prevent birds from entering landfill sites, picnic areas, and other areas [54]. The effectiveness of this method varies between bird species and has had more positive results on waterbirds [97].

Overhead nets do not need continuous attention from a human. Birds do not become habituated to them. Moreover, when birds manage to pass through the mesh, they become disorientated and susceptible to other dispersal techniques, such as hunters or air cannons. Although it is a solution that makes it difficult to collect fruit from a tree protected by nets, it solves the problem of the presence of birds in a permanent way. The main negative aspects are the associated costs and the difficult application in large areas [23].

5.2. Foam

Foam is a method that replaces soil when it comes to covering up an area. It is not a well-researched method, nor a widely used one, but from the few tests that have been carried out, it was possible to observe that the birds had a certain aversion to entering the foam covering [23].

5.3. Bird Balls

Bird balls, shown in Figure 4b, is a method that prevents birds from accessing aquaculture tanks. It works by placing balls on the tank surface. It helps by hiding the area beneath the spheres, thereby deterring birds from being attracted. Because it consists of several independent spheres, it is adaptable to obstacles that may arise in the water without affecting the positioning of the other spheres [23].

5.4. Summary

A summary of the studies that have considered exclusion deterrents is provided in Table 4.

Table 4. Summary of the studies using exclusion deterrents.

6. Habitat Modification

Habitat modification is the removal or alteration of the natural characteristics of a site. It may include trees and shrubs, the removal of ponds, planting in areas without flora, planting crops that are not attractive to birds, such as tall grass, eliminating possible nesting areas, the use of exclusion methods barriers, and even chemical agents used in the birds’ natural foods.

6.1. Tall Grass

The effectiveness of using tall grass, shown in Figure 5a, can be explained because it prevents birds from viewing and accessing food. Nevertheless, some bird species can feed even if tall grass exists [98]. In addition, there are areas, such as airports, where it is not possible to have tall grass, because it creates problems for clearly viewing the lights.

Figure 5. Habitat modification: (a) tall grass; (b) Benomyl.

Dekker and Zee [99] performed an experiment with “poor grass”, which was a mix of wildflowers and a small number of grasses. In a five-year period, they concluded that the number of birds in these areas was similar to the one observed when long grass was used. However, it changed the type of bird species that frequented these areas to smaller ones.

Modifying the habitat with a plow would bring worms to the top, which are food for many birds, making the area more attractive to birds. Therefore, it is advisable to use this method at times of less bird activity [100].

6.2. Fungicides

Benomyl and Tersan, shown in Figure 5b, are fungicides used to treat lawn fungus problems. These products have low toxicity for birds and have positive results in reducing earthworms [101]. Since earthworms are bird food, if they disappear, the birds will have to look for food elsewhere. Terraclor, which is also a fungicide, showed positive results in significantly reducing the number of earthworms at the Vancouver International Airport [101].

These products have been stopped from being used to reduce pesticides in the environment.

6.3. Other Techniques

Water Removal

This approach is based on the principle of removing the water to prevent the birds from resting there. Gulls (Larinae) use water areas to rest. By removing the water, the area is no longer attractive to the birds [102].

Feeding Changes

The feeding zone limits the presence of birds in each area. A study [102] reported that, on a landfill where some 60,000 gulls were believed to live close, they were dispersed to the surrounding landfills due to the lack of food.

6.4. Summary

A summary of the studies that have considered habitat modification methods is provided in Table 5.

Table 5. Summary of the studies using habitat modification methods.

7. Removal Deterrents

This method consists of catching birds and releasing them away or eliminating them, either with traps, poison, or the use of lethal ammunition. It is a method that requires skills to be used, because it may use materials that can be lethal to humans as well. Using lethal methods would only work in the short term and only reduce the bird’s local population.

7.1. Traps

Traps, shown in Figure 6a, are one of the oldest methods [103]. They consist of cages and nets [104,105,106] that are used to capture the birds so that they can be released as far away as possible and in suitable habitats so that they do not return. But they can also be used to capture the bird and then kill it. There is another type of trap, called the pole trap, but it has negative results in saving birds, and it is illegal in many countries.

Figure 6. Removal deterrents: (a) traps; (b) live ammunition shooting; (c) surfactants; (d) falconry.

The operation of the traps depends on the number of birds in the population, the amount of food that is outside the trap, and whether the birds are already used to the presence of traps. Shake [103] found that traps were not effective in red-winged blackbirds (Agelaius) in corn fields, due to the number of birds in the group. Mott [93] noticed that when a small group of green-backed herons (Butorides virescens) was captured and released a few kilometers away, they did not return.

7.2. Live Ammunition Shooting

This is a method that consists of using lethal ammunition, as shown in Figure 6b. It is a method commonly used at airports to eliminate seagulls. It has limited effectiveness and acts as a deterrent. It was seen that, in the short term, it eliminated some gulls and frightened others, but, in the long term, they returned [9,107,108].

7.3. Surfactants

Surfactants, shown in Figure 6c, are chemical elements that keep birds away but in a non-lethal way and without causing damage to them. These chemicals are used with water cannons or sprinklers to control the birds [109,110,111,112]. This method works as follows: The water cannon spreads surfactants that penetrate the feathers, and, once wet, the body temperature of the bird lowers, and, depending on the environment, the bird may even die.

The most used surfactant is PA-14, and, in [113], it was used to control blackbirds (Turdus merula) and starling roosts (Sturnidae), but it did not cause any reduction in the local bird population.

7.4. Falconry

Falconry, shown in Figure 6d, is used to chase and eventually kill the birds in the area. Falconry was widely used in airports and aerodromes, with positive results. However, it was necessary to change its “launching” origin so that it would not cause habituation to the birds [107].

Heighway [107] found that, when using a set of eight peregrine falcons that were trained and commanded by two trainers, it took about two years to control a population of gulls (Laridae) [86,107]. Gulls (Laridae) show no signs of habituation to hawks [114]. Hahn [115] concluded that the use of falconry is not recommended in civil airfields.

This method has also been used to prevent gulls (Laridae) from nesting in Toronto [116]. To do this, the predatory birds were attached to perches and only occasionally allowed to fly. Falconry has also proven useful in preventing nesting by Canadian geese (Branta canadensis) in Canada, whereas other techniques such as pyrotechnics had no effect [27,28,29]. Another study [117] concluded that the use of goshawks (Accipiter gentilis) was not effective, since, when the wood pigeons (Columba palumbus) are dispersed, they will settle back down and feed normally.

In [118], a team visiting a landfill several times a day observed that the effectiveness of the deterrent methods varied depending on the time of day and the habituation of the gulls. To reach these conclusions, the team used various techniques, including firecrackers, falconry, shooting dead gulls into the air, and firing lethal ammunition [58,118]

Moreover, falconry only achieved positive results if it was practiced by well-qualified trainers. It is only possible to use this method when there is no harsh weather, rain, or strong winds and fog, which makes it difficult to control the gulls because they feed when these conditions occur [23,119,120]. Given that it is an unscheduled technique, it can be more effective. However, its use is recommended to reinforce other deterrents [23].

7.5. Summary

A summary of the studies that have considered removal deterrents is provided in Table 6.

Table 6. Summary of the studies using removal deterrents.

8. Other Deterrent Techniques

8.1. Lure Area

Lure areas, shown in Figure 7a, are created to attract and trap birds so that they are not in areas where they should not be [121]. The best option is using food to attract birds. In agricultural fields, this method is applied through perches to intercept the birds. Thus, the birds are distracted from the crops and feed on the perch. Nevertheless, to attract birds, it is necessary to take into consideration the distance to which the birds should not go.

Figure 7. Other techniques: (a) lure area; (b) magnets; (c) microwaves; (d) laser.

These attraction areas have proved to have positive results with waterfowls and blackbirds [121].

8.2. Magnets

This approach requires two magnetic devices, shown in Figure 7b, hanging along a wire. This wire is hung along places that the birds frequent for both nesting and resting. This device creates a magnetic field that disorients the birds, which will then avoid the areas that have these devices. This can be explained by the fact that birds use the earth’s natural magnetic field to orient themselves [122,123,124,125].

Belant and Ickes [126] tested this method, and it proved to be useless in deterring European starlings (Sturnus vulgaris). More testing is needed to confirm the effectiveness of this method, since it has only been proven to disorient birds and not to disperse them.

8.3. Microwaves

Microwaves, shown in Figure 7c, are electromagnetic waves with frequencies ranging from 300 MHz to 300 GHz that can cause stress, discomfort, and disorientation [122,123,124,125]. If the energy caused by electromagnetic fields is too high, it can cause physical problems for birds, which leads to the birds avoiding them. Humans can detect these energies below 1 mW/cm² and at maximum power densities bellow 100 mW/cm² [127,128]. If the power is higher, thermal changes begin to be felt. In birds, these changes occur at a power of 50 mW/cm² [129]. The effectiveness of this method is questionable, but if the power is increased, the effect will be felt. For example, at a power of 10–50 mW/cm², there may be temporary muscular and neurophysiological problems [130,131]. These problems affect the ability to extend the legs and wings, so birds collapse [130,131].

In [131], tests were performed with hens (Gallus gallus domesticus). One feeder was exposed to a radiation intensity of 40 mW/cm² while the other was not. The hens (Gallus gallus domesticus) chose the feeder without radiation. The hens only returned to the first feeder 4 days after removing radiation from it. Furthermore, they avoided the feeder when radiation was applied to it again.

Some studies have concluded that radars can affect birds [132,133,134,135,136]. Short et al. [76] studied the possibility of using radar signals to disperse birds without the radiation reaching levels considered dangerous to humans and birds.

8.4. Laser

Lasers, shown in Figure 7d, produce electromagnetic waves in the visible and infrared light frequency ranges. These waves associated with the emitted light can cause birds to feel sick [23]. This decreases the possibility of birds staying in these places.

Lasers were suggested by Lustik in [137]. Although the tests showed that the laser was effective on starlings (Sturnidae), mallards (Anas platyrhynchos), and gulls (Laridae), the beam had to be aimed at specific areas of the bird. For example, if it was aimed at the feathers, they would not react, and if the laser managed to reach a certain temperature, there was the possibility of igniting the feathers. A particular test showed that the use of a flashing light directed at some birds could cause hemorrhages in their eyes, but the gulls showed no discomfort or reaction, not even with the light pointed directly at their eyes [137,138]. In [139], Mossler performed tests on gulls using a helium-neon laser. In this case, the gulls showed some limited behavioral reactions, but it was not enough to disperse them or prevent them from feeding.

Although lasers are a method with positive results, they can be dangerous to human beings [23], so their use is not recommended.

8.5. Summary

A summary of the studies that have considered other deterrent techniques is provided in Table 7.

Table 7. Summary of the studies using other deterrent techniques.

9. Discussion

This section draws the main conclusions from this research. Current gaps are identified and strategies for future research are proposed. Table 8 summarizes the different methods and techniques used as bird deterrent solutions for crop protection.

Table 8. Summary of different methods and techniques used as bird deterrent solutions.

Scarecrows: Scarecrows are a very versatile tool that can be applied both on land and water; they are very mobile and cheap to build. They can be combined with other bird deterrent techniques to improve performance. In the long term, they are not effective, so they are best suited for occasional bird invasions and should be used in smaller areas.

Reflectors and Reflecting Tape: Reflective tapes are easy to install and can quickly be transferred to another area. Their effectiveness can be improved when combined with other bird deterrent techniques, so their use in agriculture and at airports with more moderate use is recommended.

Hawk kites and balloons: Kites and balloons can be easily deployed and can be moved to other locations with ease, but have many limiting factors such as strong winds and rain or even the difficulty to keep the balloons inflated. These techniques must be complemented with other approaches to increase their effectiveness. Therefore, this technique is recommended only in short-term situations.

Dead bird models: When used alone, they can be effective for a short time, but they are perfect for integrating into a bird deterrent program.

Aircraft: As discussed above, this type of technique is not recommended at all. It is too risky for the aircraft tripulants, because birds can do real damage to the aircraft. That is why it is necessary to deter birds from airports.

Radio-Controlled Aircraft or UAV: Some advantages of this implementation are that the time it takes the birds to get used to this technique is much longer than the techniques mentioned above. Moreover, making several passes with the aircraft can even cause the birds to leave the site completely. It is also applicable to a wider range of bird species. Disadvantages are that it requires a skilled operator and is very labor intensive. There is also the need for landing and landing areas, and it cannot be used in adverse weather conditions. On the other hand, if UAVs are used, a human pilot is not required, but the use of optimization algorithms is necessary to improve their efficiency and autonomy.

Lights: Flashing and strobe lights can be useful for scaring birds, but they can be even more effective when used in conjunction with other techniques. Spotlights may not be as effective. because they can attract birds in certain weather conditions. They are easy to install in places such as airports and agricultural fields. They are not expensive and are quite effective at scaring away certain bird species at night. Their efficiency as a bird deterrent has not been proven.

Shotguns and rifles with real ammunition: This method is not recommended for the safety of humans, as someone could be hit by the shot. It requires authorization and knowledge to handle these weapons. Furthermore, it is costly, as the ammunition used is single-use and is relatively expensive.

Pyrotechnics: Pyrotechnics are among the most widely used approaches when it comes to bird dispersal. It is a highly effective technique, but only in the short term, due to the habituation it causes in the birds. Thus, birds stop being frightened by the noises that these devices produce. They are often used more in the form of rifles or pistols to facilitate their mobility. It is believed that the effectiveness of this method may vary with different species of bird. To be more effective, this method should be used only when many birds are grouped together. Pyrotechnics have many advantages such as their range; the blast has a stronger shockwave than a shot, so it also helps scaring birds away, and they can be highly effective when used in conjunction with other deterrents. It also has disadvantages, such as the possible death of birds. It cannot be used in all areas, since if it is used in areas with dry vegetation, it can cause fires. It requires highly skilled labor to reduce the high risk of handling. Another disadvantage of this approach is that it produces a lot of waste, such as cartridges from the devices used.

Air cannons: Cannons have proven to be effective in large areas and do not require continuous attention from the owner. However, they are only effective for a brief time. Furthermore, cannons with less safety devices should not be used in certain places, because they present a fire hazard.

AV-alarm: The positive side of this device is that it does not need constant attention from the owner, and, if it is moved frequently, it will become more effective. On the downside, birds can easily become accustomed to sounds, and the sounds emitted by these devices can put the bird’s life at risk. These devices can also carry risks to human health. So, hearing protection equipment must be worn when one is near one of these devices in operation.

Predators sounds: This method is a little uncertain, because it can both disperse or attract birds. Although there have been some positive results reported in studies, it is not possible to confirm its effectiveness.

High Sounds: Like the other auditory deterrents, this method ceases to be effective within a short time. Furthermore, this method is not very human-friendly, as these sounds can also cause severe hearing damage.

Ultrasound and Infrasound: This method would be quite good because it would not affect humans, since they do not capture such frequencies and, therefore, would go unnoticed. However, it is ineffective, because birds also do not capture these types of frequencies.

Tactile deterrents: It is difficult to accurately assess how effective sticky chemicals are, due to the lack of studies that evaluate their effectiveness. They require some work to be implemented, which includes studying all corners, areas, and poles where birds may land and treating all of them. They are estimated to last for a year or so, depending on the weather conditions. They have proven not to be effective in temperatures below −9 °C. Sticky materials are not exactly pleasing to the eye, so this may limit their use.

Behavioral deterrents: This method requires several steps before it will work. It requires getting the bait and the poison, the right dosing, and waiting for the birds to be attracted to the bait. Behavioral-alteration-type chemicals are recommended to be part of a bird repellent program. However, some limitations apply to the use of this technique at airports. Since the bait can attract birds into the airport at peak traffic times, this is not recommended at all.

Methyl Anthranilate—ReJeX-iT: It has the potential to repel a limited spectrum of bird species. It is natural and has a low degree of toxicity. However, one must always pay attention to the formula applied, its concentration, and how regularly it is applied. Cost can also be a negative factor, as it can get expensive if a large area needs to be covered. Nevertheless, its use is recommended.

Overhead Netting: It is method is recommended for small areas that cannot be monitored continuously by a human.

Foam: Its effectiveness depends on weather conditions, such as rain or wind, which could eliminate the foam or remove it. It can be used in small areas.

Bird Balls: Its operation depends on wind conditions, because it is a light material that is easily moved with the force of the wind. It is easy to use and has a low cost. Since it is a new method, there are no studies that assess its effectiveness.

Tall Grass: This method is useful because it reduces the number of species. However, it becomes dangerous in certain situations, because, in this type of habitat, there is food for large birds such as hawks and owls, and, in places such as airports, this may lead to negative consequences.

Traps: This method can be a time-consuming and expensive process. Depending on the complexity of the trap, it may require skilled labor. Furthermore, it is a solution that may work only in the short term.

Live Ammunition Shooting: Lethal ammunition is only used to increase the effectiveness of other combined techniques. This method must be used sparingly and requires specific licenses.

Surfactants: Water sprays, with or without surfactants, are recommended as a lethal method of bird control. It is also used in the short term to disperse bird flocks, but pyrotechnics are preferable for that case.

Falconry: Since hawks are a real threat, the birds are not used to their presence. Since it is an unscheduled technique, it is more effective. However, qualified people are required, and there is the impediment to flying in adverse weather conditions. The use of falconry is recommended to reinforce other deterrents.

Lure Area: It requires a lot of work to study the birds’ flying patterns to implement the lure area.

Magnets: It is not recommended due to a lack of studies that prove that birds are deterred by this method.

Microwaves: From the studies and tests carried out, it was concluded that it would only be effective to use radiation if it reached levels that were already dangerous to human health. Therefore, the use of this method is not recommended at all.

Laser: Although it is a method with positive results, the energies created by them would be dangerous for human beings, so its use is not recommended.

10. Conclusions

Of the various pests that exist for agriculture, birds are one of the biggest and most damaging to farmers, and possibly the most difficult to control. This survey presented a comparative analysis of bird deterrent techniques for crop protection. It introduced the related concepts. Then, visual, auditory, chemical, exclusion, habitat modification, removal, and other deterrents solutions were presented. Their results, strengths, and weaknesses were discussed. Finally, current gaps were identified and perspectives on future developments were discussed.

Despite the availability of bird deterrents, there are still many challenges for effectively protecting crops from bird damage. These challenges include the need for cost-effective solutions, the ability to adapt to changing bird populations, and the potential for negative impacts on non-target species and the environment. Nevertheless, there are also several opportunities for improvement in bird deterrent solutions for crop protection. These opportunities include the development of new and innovative deterrents, the integration of multiple deterrents for increased effectiveness, and the use of technology to enhance the monitoring and evaluation of deterrent effectiveness.

Thus, bird deterrent solutions for crop protection are a complex and multifaceted issue, and there is a need for continued research and development to improve their effectiveness and minimize negative impacts.

The research that is presented in this paper is a first step in an ongoing effort to propose, in the context of smart farming, a new bird deterrent technological solution based on the concepts of the Internet of Things (IoT), wireless mesh networks, and smart drones.

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Bird Deterrent Solutions for Crop Protection:

1. Introduction

2. Visual Deterrents

2.1. Scarecrows

2.2. Reflectors and Reflecting Tape

2.3. Hawk Kites and Balloons

2.4. Dead Bird Models

2.5. Aircraft

2.6. Radio-Controlled Aircraft or Unmanned Aerial Vehicle

2.7. Lights

2.8. Summary

3. Auditory Deterrents

3.1. Shotguns and Rifles

3.2. Pyrotechnics

3.3. Gas Cannons

3.4. AV-Alarm

3.5. Predator Sounds

3.6. High-Intensity Sounds

3.7. Ultrasounds

3.8. Infrasounds

3.9. Summary

4. Chemical Deterrents

4.1. Tactile Repellents

4.2. Behavioural Repellents

4.3. Methyl Anthranilate—ReJeX-iT

4.4. Summary

5. Exclusion Deterrents

5.1. Overhead Netting

5.2. Foam

5.3. Bird Balls

5.4. Summary

6. Habitat Modification

6.1. Tall Grass

6.2. Fungicides

6.3. Other Techniques

6.4. Summary

7. Removal Deterrents

7.1. Traps

7.2. Live Ammunition Shooting

7.3. Surfactants

7.4. Falconry

7.5. Summary

8. Other Deterrent Techniques

8.1. Lure Area

8.2. Magnets

8.3. Microwaves

8.4. Laser

8.5. Summary

9. Discussion

10. Conclusions

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