How Do Airports Keep Birds Away?

When a bird collides with an aircraft it is called a bird strike. Bird strikes can result in devastating accidents and can lead to significant aircraft damage. Globally, wildlife (birds, mammals, etc.) strikes killed more than 301 people and destroyed over 298 aircraft during the period between 1988 and 2021.

Probably the most famous bird strike incident is the one involving Captain Chesley Burnett Sullenberger III that occurred on January 15, 2009, when US Airways Flight 1549 (an Airbus 320) with 155 persons on board made a forced landing in the Hudson River after ingesting Canada geese into both engines at 2,900ft above ground level after departure from LaGuardia Airport in New York.

Whilst it seems that bird strike incidents are on the rise, fortunately, very serious incidents are rare. The rise in bird strike incidents seems to be related to increasing populations of large birds and increased air traffic by quieter, turbofan-powered aircraft.

In this article, I take a look at why birds are attracted to airports, explain why it’s so important that airport operators control birds to reduce the likelihood of bird strike incidents, and look at some of the strategies employed to manage birds in and around airports.

How Do Airports Keep Birds Away?

Why Birds Flock Around Airports

There are many reasons why airports make good homes for birds:

  • Food sources: Natural food sources are found in airport grasslands and water bodies (e.g. insects, plants, nuts, and berries), and there are also plenty of man-made food sources such as food waste
  • Open terrain: Flat, open terrain, including airfield grassland, runways, taxiways, aprons, and paved surfaces, may all create secure areas for birds and some wildlife
  • Buildings and structures: Aircraft hangars, terminal buildings, airport rescue and fire stations, old aircraft, lighting, and signage structures all provide roosting sites, perching opportunities, or possible nest sites
  • Landscaping: Landscaping developments have the potential to create dense vegetation that may become a roost, provide an abundant autumn and winter food supply, and create standing water or watercourses that attract gulls and waterfowl
  • Water bodies: Open, standing water, such as balancing ponds, reed beds, watercourses, drainage ditches, or river channels, may attract large flocking birds, including ducks, geese, and swans

Birdstrike Incidents in the UK and the USA

The UK CAA report on bird strikes covers the period from 2012 to 2016. This report shows that in 2016 there were almost 3,000 bird strikes in the UK compared to around 2,200 in 2016.

The CAA classified reported bird strikes as ‘Confirmed’, ‘Near Miss’, or ‘Unconfirmed’. An unconfirmed bird strike is one where there was a reported collision between a bird and an aircraft but no evidence of the collision was found (bird remains or aircraft damage). Around 60% of the reported bird strikes were confirmed, and fortunately, 95% of confirmed bird strikes resulted in no aircraft damage. However, a bird strike even without damage is expensive for airlines as the aircraft has to be taken out of service, checked, and tested.

In the UK the majority of bird strikes occur during the summer months. Over 55% of UK 2012-2016 bird strikes occurred in the four months between June and September.

The UK data shows that the majority of bird strikes had no immediate safety impact with 94% of strikes having no operational effect. One percent of strikes resulted in an aborted take-off and 2% resulted in a return to the airport or a diversion to another airport.

Exactly when bird strikes occur, in terms of the flight phase, is not known in 44% of UK incidents. However, 46% of known incidents occur when the aircraft is under 200 ft on landing, or under 500 ft on take-off. That means that 85% of known incidents occur on take-off and landing, explaining why bird control at or close to airports is extremely important.  

The US FAA/USDA published a report on bird strike incidents for the period from 1990 to 2021. This study showed that about 42% of bird strikes with commercial aircraft occurred when the aircraft was at 0 feet, 71% occurred at 500 feet or less, and 92% occurred at or below 3,500 feet. But it seems that strikes can occur at almost any height used by commercial aircraft – the record height for a reported bird strike involving a commercial aircraft in the USA is 31,300 feet.

The US FAA/USDA report also showed that in 2021 there were around 15,600 reported bird strikes in the USA. Of these, around 4% resulted in aircraft damage, similar to the UK.

Over the 32-period of the US study it was found that the vast majority of bird strike incidents occurred during take-off or landing, with 33% during the take-off run and climb, and 60% during approach and landing. 

The Importance of Controlling Birds At Airports

The importance of controlling bird populations at or around airports boils down to two facts:

  • For a whole variety of reasons airports attract birds and provide good ‘homes’ which can supply plenty of food in an environment with few natural predators
  • Bird strikes tend to occur mostly at the critical flight phases of take-off and landing; the UK CAA study showed that of the bird strike incidents where the time of the strike can be identified, 85% of strikes occurred during take-off or landing and in the USA the proportion is over 90%

These key factors are supported by evidence that shows, in the USA at least, that the populations of certain large bird species such as turkey vultures and black vultures, each weighing around 2 kg, are increasing significantly. And, of course, larger birds are likely to have more catastrophic bird strike impacts compared to smaller birds.  

Also, the number of 3- and 4-engined aircraft has reduced drastically in recent years and these aircraft now account for only around 5% of total commercial aircraft. In the event of multiple-engine ingestions, aircraft with two engines may have vulnerabilities not shared by their three or four-engine-equipped counterparts.

Airport Bird Control

Bird Management And Control at Airports

Some of the less conventional, and less common, methods of controlling birds at airports include trained dogs and birds of prey.  This method is rare owing to the costs of looking after the animals and birds. Dallas-Fort Worth International Airport uses birds of prey to chase roosting birds from a parking lot.

An alternative to live birds is the use of bird effigies. Turkey vultures don’t like the sight (or smell) of dead vultures, and a dead or stuffed vulture can be quite effective in vacating an area. Gulls and ravens can also be deterred using this method.

Unmanned aircraft systems built to look like falcons are an emerging option, but they are expensive and require advanced training to operate.

One US airport operator has deterred gulls by adding grape flavor to water pools to keep gulls out of the water that has pooled after heavy rains. The gulls don’t like the taste. Other airports use grape-seed extract as a non-lethal, eco-friendly, and budget-friendly method to deter geese (and deer).

More standard methods employed by airports include the following:

  • Cutting the airfield grass to an appropriate optimum height (20-30cm), and keeping it weed-free, can be one of the most effective measures of bird hazard control.
  • Habitat management is also important including pest/insect control to reduce natural food sources, moss control (moss can harbor a variety of insect food sources), tree management to deter nesting, and netting of water bodies to deter water-loving birds.
  • Plastic ‘bullets’ – paintballs and other plastic projectiles fired at large birds such as geese can drive these birds away. This is an effective and non-lethal method.
  • Some airports use remote-controlled cars and boats to flush out and deter birds.
  • Pyrotechnics and cannons – birds don’t like fireworks, which is probably one of the most used tools airports use. Propane cannons are also effective. Birds can get used to both methods, especially if used at the same time every day so airports have to employ a varied schedule when employing sound-driven deterrents.
  • Broadcasts of distress calls to lure birds to the source and away from air traffic are not always reliable because not all birds have distress calls, and so often this method is combined with another.
  • The FAA recognizes that lasers can help create separation between birds and aircraft. They can be very effective if used correctly and for the right species. Trials have shown that green lasers may be a useful bird dispersal tool in bird control operations as part of a wider bird hazard management program.
  • Manual dispersal by humans (arms flapping etc.) is useful as a supplementary method, especially where noise deterrents may cause a nuisance to nearby residents.

Summary

Controlling bird populations at and around airports is a vital operational safety requirement for all airport operators.

Bird strikes are daily occurrences, but fortunately, catastrophic incidents are rare, and around 95% of strikes result in no aircraft damage. The importance of bird control at airports is underlined by the fact that the majority of strikes occur during aircraft take-off and landing – up to 90%.

Airports have a wide variety of techniques that they can employ to deter and manage bird populations. The next time you are at an airport, take a closer look and see if you spot any of the static or active measures in place!

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