WHEN a bird comes up against an aeroplane, the result is not always pretty, sometimes even for the machine.
But various initiatives, from mimicking birds' distress calls to covering canals, has seen Changi Airport halve the number of such wildlife strikes from 13 to around seven a month in the last year.
The most serious incident to date happened last June, when a Brahminy Kite, a medium-sized bird of prey, flew into the engine of an Airbus A320 shortly after its wheels touched the ground.
The arriving plane's schedule was delayed by around two hours, as airport staff removed the carcass and inspected the aeroplane to ensure it was safe to fly.
Such incidents are rare at Changi, which has more than 27,000 flights per month. Most wildlife strikes are minor, with little or no damage to aircraft.
Yet they can pose significant problems, said Changi Airport Group (CAG) vice-president of airside management See Seng Wan.
In 2009, in what has been labelled the "Miracle on the Hudson", a US Airways plane struck a flock of geese after take-off and lost power in both engines. Its pilot made an emergency landing in New York's Hudson River. All 155 occupants were safely evacuated.
The issue of wildlife strikes is more pertinent for Changi which, given its proximity to wooded areas and the coast, naturally attracts animals. Birds commonly spotted there include mynas, crows and egrets.
The largest is the white-bellied sea eagle, which weighs up to 4kg. Other wildlife include bats, snakes and dogs.
To minimize the risk of wildlife strikes, CAG has ramped up a range of initiatives to keep birds and other animals out. Its wildlife management team, which comprises 12 officers, began conducting four to six two-hour patrols a day last year, compared to eight times a month previously.
Birds spotted near aircraft movement areas are dispersed by broadcasting bird distress calls from the patrol vehicle or through loudhailers. Officers can select up to 20 calls that mimic the sounds made by different species when in distress.
All bird sightings and subsequent actions taken are recorded in a system, so hot spots can be identified.
There are specific measures for different birds. Distress calls are mainly for birds that flock, while anti-perching devices were installed on railings in three locations last year to discourage larger birds.
Added Mr See: "Birds and animals are always looking for two things, food and shelter. So we also try and eradicate their source of food."
The CAG horticulture team ensures no fruit-bearing trees or plants that attract animals are planted within the airport.
Its engineering team has a grass cutting and maintenance programme that keeps the 600ha of turf around the airport unattractive to birds. For instance, grass is not cut when it is wet, so that the soft topsoil along with its insects will not be churned out and attract birds, said Mr See.
All dustbins are covered so animals cannot forage for food. Staff are also forbidden from eating or drinking airside, where aircraft can access, and those caught face a fine.
CAG works with various partners such as the National University of Singapore's Raffles Museum of Biodiversity Research, which conducts a quarterly census to determine the amount of bird activity within the airport.
Another partner is the Nature Society, which shares its knowledge of local bird species and helps identify unknown carcasses.
Its bird group chairperson Alan Owyong said the key solutions are to remove nesting sites and food sources. He has also advised CAG to cover bodies of water, which attract birds such as herons, and it has taken action.
The CAG has awarded a contract to cover these bodies of water, which include canals, with netting. Its staff also remove silt and floating plants from these areas.
All these measures have brought the number of reported bird strikes down by half, and without the CAG having to cull birds in the past three years.
Still, it is currently assessing new methods to manage wildlife, such as long-range acoustic devices and grass sprays which help keep birds away.
Said CAG spokesman Robin Goh: "Animals are naturally able to adapt, so we constantly explore new measures to manage wildlife for the safety of our flights and passengers - which is always top priority."