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Managing the risks of bird strikes

Posted: 3 April 2007 | Dr. Richard A. Dolbeer, U.S. Department of Agriculture and Chairperson, Bird Strike Committee USA | No comments yet

When making a list of the activities that an airport manager must oversee, most people would never consider a program to manage birds and other wildlife. However, aircraft collisions with birds (bird strikes) at airports are an increasing economic and safety problem for the air transport industry worldwide. Based on a recent analysis of economic data by Dr. John Allan of the UK’s Central Science Laboratory, bird strikes are costing the worldwide air transport industry over $1.2 billion (USD) every year. Economics are not the only concern. Over 200 people died as a result of bird strikes with civil and military aircraft from 1988-2006. And birds are not the only problem. A recent survey by the author uncovered over 630 damaging strikes to aircraft involving terrestrial wildlife (e.g., deer, wild dogs) in 22 countries. In the USA alone, 17 civil aircraft have been destroyed by collisions with deer since 1983.

When making a list of the activities that an airport manager must oversee, most people would never consider a program to manage birds and other wildlife. However, aircraft collisions with birds (bird strikes) at airports are an increasing economic and safety problem for the air transport industry worldwide. Based on a recent analysis of economic data by Dr. John Allan of the UK’s Central Science Laboratory, bird strikes are costing the worldwide air transport industry over $1.2 billion (USD) every year. Economics are not the only concern. Over 200 people died as a result of bird strikes with civil and military aircraft from 1988-2006. And birds are not the only problem. A recent survey by the author uncovered over 630 damaging strikes to aircraft involving terrestrial wildlife (e.g., deer, wild dogs) in 22 countries. In the USA alone, 17 civil aircraft have been destroyed by collisions with deer since 1983.

Birds flock to airports

Highly successful environmental programs funded by governmental organisations during the past 35 years (e.g., pesticide regulation, expansion of wildlife refuge systems, wetlands restoration), coupled with land-use changes, have resulted in dramatic increases in populations of many bird species that pose risks to aviation in North America and Europe. For example, 24 of the 36 largest (>1.8 kg) bird species in North America have shown significant population increases in the past 30 years and only 3 species have shown declines. Many countries outside of Europe and North America have followed suit with expanded wildlife conservation programs in recent years that are resulting in increased bird populations. As the human population continues to expand, many birds have adapted to urban environments. These birds have discovered that airports, with large areas of grass and pavement isolated from people, are attractive habitats for feeding and resting. To make matters worse, modern aircraft, with quieter engines, are less easily detected and avoided by birds.

ICAO establishes standards

In 1990, the 190 member nations of the International Civil Aviation Organization (ICAO) adopted, in Annex 14 to the Convention on Civil International Aviation, three recommended practices regarding bird hazards to aviation. These recommended practices were that authorities:

  1. assess the extent of the risk posed by birds on and in the vicinity of airports
  2. take necessary action to decrease the number of birds
  3. eliminate or prevent the establishment of any site in the vicinity of the airport which would be an attraction to birds and thereby present a danger to aviation.

Because of the increasing threat to aviation worldwide caused by birds, ICAO member nations voted to make these recommended practices into ICAO Standards, effective November 2003. This action makes these practices a mandatory component of the standards that airports must operate under and represents a significant challenge for many airports throughout the world.

Airport authorities should also recognise that because of the ICAO standards and advances in our ability to manage bird risks at airports, bird and other wildlife strikes are no longer automatically considered an “act of God” for which nothing could have been done. Increasingly, airport authorities are being taken to court in the aftermath of damaging strikes occurring in the airport environment. Plaintiffs are demanding that airports demonstrate “due diligence” in the risk management of bird strikes.

Assessing the risk

To comply with ICAO standards, airports first need to conduct a Wildlife Risk Assessment and, based on the findings of the assessment, develop and implement a Wildlife Risk Management Plan. A Wildlife Risk Assessment typically entails documentation of the species, numbers, and behavior of birds and other wildlife using the airport and immediate surroundings. These systematic surveys by a qualified field biologist should document bird activity over the course of an entire year because species, numbers and behavior can change dramatically from season to season. These surveys also should document the habitats and sources of food that attract birds to the airport.

Once the information from the systematic surveys is compiled, an analysis can be done to rank the species posing the highest risk to aircraft safety at the airport based on numbers, body size, flock size, behavior, and time spent in aircraft movement areas. Examination of past airport-specific and national bird strike data can also help determine which species are most likely to be struck and to cause damage. This formal risk assessment is critical because a year-long survey typically will document 50 to 100 bird species using an airport. Obviously, management efforts need to focus on those species posing the greatest risk to aircraft.

For example, bird surveys during a risk assessment at a USA airport revealed a potentially hazardous species (American crow) frequenting the airport throughout the day in relatively large numbers. However, a closer examination of the behavior and flight patterns of these birds revealed that they posed a low risk because they stayed away from runways and were adept at avoiding aircraft. In contrast, Canada geese and vultures were less frequent visitors to the airport but posed a much higher risk because of their larger size, diminished ability (relative to crows) to detect and avoid aircraft, and their daily flight paths across runways going from night time roosting areas to daytime feeding sites.

Managing the risk: food, water, shelter

The Wildlife Risk Assessment forms the basis for developing a Wildlife Risk Management Plan. Birds are attracted to an airport for at least one of three reasons: food, water, and shelter. Thus, the foundation of a Wildlife Risk Management Plan for any airport should be the implementation of programs to minimise food, water and shelter that are attracting birds posing the greatest risk. These habitat management activities may involve removal of trees used as perching and roosting sites by raptors and starlings or planting varieties of grass, such as endophytic fescues, that are unpalatable to grazing birds such as geese. To discourage gulls and other scavengers, garbage dumps should be prohibited within 5 km of airports, and food waste on the airport should be stored in covered containers at all times. Water is a magnet for many bird species. Covering storm-water detainment basins and improving drainage to eliminate standing water will help discourage ducks, geese and other waterbirds that pose a high risk to aircraft. If habitats and food that are attractive to high-risk bird species are not minimized or eliminated, then active control efforts (discussed below) will provide only temporary relief at best.

Managing the risk: active control

The second component of the Wildlife Risk Management Plan should cover the use of techniques to disperse or remove hazardous wildlife that intrude on the airport. There are a variety of techniques that can be used to disperse birds: pyrotechnics fired from hand-held launchers, recorded bird-distress calls that were broadcast from vehicle-mounted speakers, trained falcons and dogs, bird-frightening lasers, chemical repellents, and dead-bird effigies to name a few.

Removal of birds by shotgun, air rifle or trap is also a critical component of risk management on many airports. Flocking birds such as gulls and geese will often habituate to continued harassment from non-lethal frightening techniques such as described above. Selective removal of a few birds by shotgun will reduce habituation by surviving members of the flock. Air rifles or traps can be used to remove pigeons from hangers and other buildings. Because most birds are protected by national laws, permits are usually needed before undertaking lethal options.

A mistake by many airport managers is focusing too much on the equipment and techniques (tools) needed to manage birds on an airport and not on the personnel that are going to use those tools. There are no devices or techniques that will, in and of themselves, solve the bird problem on an airport. The various tools described above are important. But the most critical component of a Bird Risk Management Plan is competent, trained and motivated personnel who know how to use those tools. These personnel must be knowledgeable in the identification, legal status, risk-level, and behavior of the various bird species and be skilled in deploying the various techniques in an integrated fashion. Managing birds and other wildlife on an airport is a complex endeavor that is part science and part art. It involves numerous bird species exhibiting a range of behaviors, flight patterns, and adaptabilities. For one example, skilled deployment of pyrotechnics may be effective in dispersing a flock of geese or gulls away from the airport in some situations but not in others. Pyrotechnics may be totally ineffective in dispersing species such as shorebirds, buzzards or vultures.

Another important component of the Bird Risk Management Plan is the establishment of an Airport Bird Risk Working Group or Task Force to monitor and coordinate bird-control activities at the airport. This group should include representatives not only from various airport departments but also from the local government and key landowners immediately outside the airport whose activities may influence bird numbers in the airport environment. For example, wildlife refuges, city parks, waste-management facilities, and golf courses located within 5 km of an airport may serve as focal points for birds that fly across the airport or approach and departure paths. Educating these neighbors about the risks of bird strikes may help in implementing programs to prohibit certain land uses near the airport or to minimise bird activity at the sites.

Pilots and air carriers can help

Although the management of bird risks is primarily an airport’s responsibility, there are actions that can be taken by pilots and air carriers in partnership with airports to reduce damaging strikes. Pilots have a unique “bird’s eye view” of an airport and can sometimes see bird and other wildlife activity not readily apparent to airport personnel. Thus, bird and other wildlife hazards observed at airports should be reported to ATC tower or airport operations. Likewise, when a bird strike does occur, pilots and the air carrier should endeavor to report the strike to the airport and Civil Aviation Authority. The identification of the species of bird involved in the strike is critical. Thus, remains of the bird should be frozen or otherwise preserved for identification by a local expert. After all, an airport cannot solve a bird problem of which it is not fully aware or does not understand. Documentation of the problem also is an important means of educating the public about the need to manage wildlife at airports.

Revised manual available

In 2005, the U.S. Federal Aviation Administration and U.S. Department of Agriculture jointly published a revised 347-page book “Wildlife Hazard Management at Airports – a Manual for Airport personnel” by E. C. Cleary and R. A. Dolbeer. English, Spanish, and French versions of the manual are available in pdf format at http://wildlife-mitigation.tc.faa.gov. The manual provides background material and detailed practical guidance for airport personnel involved in managing the risks of bird and other wildlife strikes at airports.

Conclusions

Many bird species that pose a risk to aviation safety have shown population increases in recent years. These birds often view airports as attractive open spaces to feed and rest. Because of these developments, ICAO member states voted in 2003 to change the recommended practices in place since 1990 to mitigate wildlife hazards at airports into mandatory standards. Airports worldwide need to ensure that they are in compliance with these ICAO standards. Integrated risk management programs that are developed and overseen by professional biologists are critical to minimize bird hazards to aviation. There also is a need for better education of pilots and air carrier personnel regarding the reporting of wildlife strikes and actions that can be taken to reduce the probability of strikes.

The Bird Strike Committees of USA and Canada meet jointly each year to provide education and training in wildlife risk management for airport personnel worldwide. The meeting also provides a forum for vendors to demonstrate products and services related to wildlife and environmental management at airports. This year’s meeting is in Kingston, Ontario, Canada, 10-13 September (details at www.birdstrike.org). Our goal in all of this is to create safer skies for all who fly – birds and people!

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