Technical | PPC92 September 2018

Being ‘birdbrained’ is meant to be an insult. Typically it’s used to describe the sort of person you wouldn’t want on your pub quiz team. Any professional pest controller with experience in bird work will tell you that there’s nothing stupid about the nation’s problem birds. Andy Baxter, MD of Birdstrike Management, investigates how understanding and controlling behaviour is key to reducing risks in this field.

SPEED READ:

• Some bird senses change depending on ecological niche 
• Flocking birds will do exactly that when in danger, while predators tend to have no learned response
• Some birds can differentiate between shotgun and gas cannon sounds
• Feral pigeons have been subjected to perhaps all possible control methods
• It is not clear how instinctive responses can be integrated into a control programme

Good bird management not only requires an understanding of the problems faced and solutions available but often the responses and behaviours of the species themselves and the effect of over utilisation or reliance on particular tools. While we may separate bird, mammal and insect groups into different types of response, the reactions to, and impacts of, control methods on individual species can vary significantly.

Deterrence of gulls may require a different strategy to that of pigeons, corvids or raptors. We all believe that our humble crows are perhaps ‘cleverer’ than pheasants - certainly, if roadside casualty levels are anything to go by this appears to be strongly evidenced! But is this all just down to the ability of different species to comprehend and react to potential threats or can individuals exhibit learnt responses?

A bird’s-eye view

Firstly, birds rely on different senses to respond to different environmental stimuli; hearing enables a response to sound, eyes to visuals etc. The evolutionary development of species, however, means that these senses vary significantly depending on the ecological niche within which a species or group of birds reside.

Raptors, for example, have evolved outstanding eyesight that enables both colour perception and excellent resolution. As a hunting species, their eyesight is concentrated on forward-looking magnified vision targeting the capture of their prey. Their prey, however, has evolved much wider peripheral vision to enable them to detect an oncoming predator early and take evasive action. At airports, for example, these factors mean that a group of lapwings foraging within a grass meadow are permanently alert to threats and can, therefore, have controlled dispersal undertaken by an airport operator by using visual stimuli.

Similarly, when a stealth predator has captured such prey, the prey response (if not immediately killed) is to struggle and respond with a distress call. Other lapwings will, therefore, approach and potentially mob a predator either for their safety or to drive the predator away. As a species that has evolved to flock together to evade predators, lapwings will therefore routinely bunch up and disperse as a single group.

Contrast this with the response of raptors. These birds are themselves hunters and the larger they get the more likely it is that they have no need or experience of responding to threats. For example, our increasing red kite and buzzard populations have all the sensitivity required but have not adapted to being hunted themselves. Controlled dispersal can prove extremely difficult with the result that any dispersal effort does not result in an escape response.

Fowl language

Understanding the ability of different species, therefore, to detect control methods and their subsequent behavioural responses is key to good wildlife hazard management.

Corvids are perhaps one of the best examples of ‘intelligent’ birds. Apart from featuring on wildlife documentaries working out the steps needed to access food, these birds do show very rapid learning behaviours. Where pest control activities occur in fields, corvids rapidly learn the range of shotguns and the difference between the sounds of a shotgun and the sounds of a gas cannon.
One presents a real threat; the other presents a perceived threat, and while both make a loud bang, the hearing ability of corvids is sufficient to detect the difference in tone. Deterrence, therefore, needs to confuse the situation to ensure that the cannons themselves are associated with the lethal threat.

Such a programme is currently being researched in relation to wood pigeons within agricultural crops to determine whether mannequins that are exchanged for identically dressed humans with shotguns can result in improved damage prevention. The ultimate scarecrow perhaps?

Putting the cat among the pigeons

The most prevalent ‘bird pest’ encountered in our environment is most likely the feral pigeon.

Ubiquitous across the country, and in many cases around the world, feral pigeons will breed regularly, be repopulated by ‘escaped’ racing pigeons and have adapted well to the human landscape. While maintaining all the abilities to perceive and respond to predator presence, feral pigeons have been subjected to perhaps every type of control attempt possible.

As a species that often lives in a busy urban environment and does not emit a traditional ‘distress call’ sound, their tolerance for many different potential deterrence methods can be high. Ultrasonic deterrence seems to produce agitation but not dispersal, and it is not clear why a pigeon would associate ultrasonic sounds with a threat.

Infrasonic sounds or ‘resonant’ sounds have been suggested as methods for physically impacting birds. Imagine the ‘thumping’ sensation produced at a rock concert or by an approaching helicopter on your rib cage. These methods appear to offer real opportunities to produce a physical stimulus to birds but are difficult to manufacture. Attempts made to create infrasound with large speakers to disperse birds had little effect.

One company has taken this theory further and suggests that a physical effect can be produced on birds by emitting sound at the correct frequency. Their findings have shown, in the laboratory at least, that an instinctive reaction can be produced that bypasses the brain. This response is inbuilt into most mammals and birds including us. The simple requirement is to minimise the time spent being ‘hurt’ by something that can create harm. In our case, when we put our hand into a flame, the pain receptor immediately sends information to the muscles to withdraw the hand upon which we think “ouch that was hot”. The learning response is one where we think “ouch that was hot” and then consciously withdraw our hand. At that point, our hand will have spent longer in the flame as we thought about the response to undertake.

It is clear that many birds have these instinctive responses, but it is not clear how those responses can be integrated into a wildlife management control programme. If the response does not create a feeling of pain or a threat that the animal wishes to avoid, will a dispersal or movement reaction occur? In other words, we are back to the original concepts of controlling problems by understanding the behaviours and reactions to stimuli and managing the reasons for problematic wildlife being present in the first place.

If birds need a place to nest, feed or rest, then eliminating the availability of those areas immediately removes the likelihood of attraction in the first place. If birds perceive a threat of any given type, then implementing that threat in a timely manner is likely to enable dispersal from an area. If, however, the attractant remains and the birds fail to perceive a threat (either through overuse or poor delivery of a control method), then the chances are our attempts at control will be thwarted. Always consider behaviours and attractants and target the most appropriate forms of control.

About Andy

Andy currently leads the team at BML as Managing Director. Andy works closely with many international airports (Heathrow, Gatwick, Schiphol) and ensures quality delivery by an exceptional team. With over 25 years’ experience having led the UK Government’s Birdstrike Avoidance Team, Bird Detection Radar Team and Wildlife Control Teams, Andy set up Birdstrike Management in 2013 to concentrate on specialist bird and wildlife risk management programmes for the aviation community.

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Source: PPC92