Earlier breeding > more young birds > more strikes with aircraft
BALTIMORE, Md. – Global warming may be involved in the explosive growth of certain bird populations, placing new pressure on airport wildlife control programs to mitigate the hazard of bird strikes to aircraft.
Although couching the findings of a recent study as “preliminary,” the peak risk of bird strikes at Dublin Airport, Ireland, has shifted to later in the year and the change appears related to climate change, said Tom Kelly of the zoology department at University College, Cork, Ireland. He was speaking at the sixth annual meeting here of the National Birdstrike Committee (BSC).
The findings suggest that efforts to control bird populations at airports must be maintained, if not strengthened, to minimize the significant danger posed by potential collisions of birds with aircraft. Not only do bird strikes inflict considerable damage to aircraft, as well as injuries and death to occupants, airports can be held liable for the cost of birdstrikes if their bird control programs are found deficient.
Above all, climate change may well be facilitating what Kelly described as “dramatic increases” in certain bird populations. This climate-related avian population growth needs to be viewed as a new threat to the successes achieved in recent years to reduce the incidence of bird strikes.
Richard Dolbeer, a U.S. Department of Agriculture (USDA) official and BSC chairman, noted that the North American non-migratory Canada goose population increased 3.6 fold from 1 million birds in 1990 to 3.6 million in 2003. Yet the incidence of goose strikes with aircraft has decreased significantly, notwithstanding the recent goose impact on an American Airlines [AMR] MD-80. The decline can be attributed to the elimination of airport habitats attractive to the geese, as well as to goose population control efforts (“ethnic cleansing,” quipped one conference participant). As measured by strikes per 1 million geese per 1 million aircraft movements, the rate for 2003 was 0.8, or more than a 40 percent reduction from the 1.4 rate in 1990.
But climate change seems to favor some bird populations, including the Canada goose, adding to what Dolbeer regards as a worsening mix of more birds flying in the same airspace with more and quieter aircraft (see ASW, Aug. 16).
At Dublin’s airport, the center of gravity, as it were, of the annual pattern of bird strikes has shifted from mid-June to the end of July.
Kelly suspects the “signatures” of climate change may well be involved. Air temperatures and rainfall at Dublin are increasing, for example. Plants are growing actively earlier in the years and maintaining their growth over a longer period of time, he noted. That extended cycle provides more food for birds.
The birds are breeding about a month earlier. While older birds learn by experience to avoid aircraft, juveniles taking to the air have led to a double peak in the annual pattern of bird strikes. The formula appears to take this form: earlier breeding leads to more young birds and thereby to more bird strikes.
Atlantic storms seem to have an effect at the airport, too. During fair weather, pelagic birds like gulls follow Irish fishermen to sea, feasting off the detritus floating behind fishing boats. Storms, though, keep the fishing boats in port. The hungry birds shift their search for food, which can take them over to the airport. “There are more gull strikes at low barometric pressure,” Kelly said, referring to the low atmospheric pressure associated with storm activity. In other words, increased ocean storminess is leading to more bird strikes on land.
More high altitude bird strikes also are being recorded. High altitude is defined as 2,000 feet above sea level and higher. Ducks, in particular, seem to be flying higher.
The overall result is a dramatic increase over the expected number of bird strikes, based on an analysis of bird strike data for Dublin airport going back to 1973.
According to Kelly, while gull strikes at Dublin are in decline, the woodpigeon population has increased. The population growth is evidenced by a considerable increase in the annual number of woodpigeon collisions with aircraft. From seven strikes annually just a few years ago, the number increased to 44 last year.
On the other hand, not all trends in bird populations seem to be associated with climate change, and other confounding variables may be at work. The lapwing population, for instance, seems to be in decline. According to John Allan of the UK’s Central Science Laboratory, there has not been one lapwing strike at London’s Heathrow airport in three years.
Nonetheless, climate change favorable to bird breeding may be adding to environmental and wetlands management programs that have contributed to huge increases in bird populations like geese and woodpigeons that pose a risk to aircraft. For airport management, the implication is evident: there can be no slackening of bird control programs.
Not only is it a safety issue, a liability risk is involved. “We’ve reviewed a number of cases where airports have been sued [by operators] due to bird strikes to recover the cost of damage,” said Dolbeer. The specter of such lawsuits can put airports “not following best practices” at risk, Dolbeer said.
One conference attendee pointed out that the bird strike rates mentioned above – reported strikes per so many aircraft movements – could serve as a basis for rating airports in terms of the effectiveness of their bird control programs. Airports could be rated on a scale of say, 1, 2 or 3, or green, yellow, red, and the rates could be posted on the Federal Aviation Admin-istration‘s Web site, and accessible both to the aviation industry and to the public. The FAA, this source noted, has not required airports to report bird strikes, urging voluntary reporting instead. However, according to numerous attendees at the bird strike symposium, the spotty, inconsistent and incomplete reporting means that only about 20 percent of all bird strikes are actually recorded.
Such a rating system for airport wildlife management control programs would certainly bring the potential liability exposure into view. >> Dolbeer, e-mail [email protected]; Kelly, e-mail [email protected] <<
Aspects of the Problem
- Aircraft-wildlife strikes are the second leading cause of aviation-related fatalities. Globally, these strikes have killed over 400 people and destroyed more than 420 aircraft. While these extreme events are rare, the potential for a catastrophic loss of human life resulting from one incident is substantial. (Source: Michael Begier, USDA, Wildlife Services, 6th annual BSC meeting)
- Thirteen of 14 bird species in North America with body masses greater than 8 pounds had significant population increases, 1970-2002. (Source: Program brochure, 6th annual BSC meeting, p. 46)
- A 12-lb. Canada goose struck by a 150-mph aircraft at lift-off generates the force of a 1,000-lb. weight dropped from a height of 10 feet. (Source: http://www.birdstrike.org/birds.htm)
- The tailfin is the only part of an aircraft built to an 8 lb. [impact] standard. (Source: Ed Cleary, Federal Aviation Administration, 6th annual BSC meeting)
Birds vs. Airplanes
Selected events in the news, 2003-2004
Jan. 9, 2003 – Medford, Ore.
Seattle flight lands safety after collision with birds breaks windshield.
June 2, 2003 – Milan, Italy
Bird collision deadly – Plane hits flock, pilots killed.
June 8, 2003 – New Delhi, India
Air India New York flight hit by bird stuck on the ground for 20 hours.
Aug. 15, 2003 – Tokyo, Japan
Seagulls close down runway at Tokyo’s Haneda airport.
Sept. 15, 2003 – Juneau, Alaska
Jet landing at Petersberg airport hits eagle.
Sept. 23, 2003 – Beijing, China
Swallows delay 100 flights at Beijing.
March 23, 2004 – Mooreland, Okla.
Duck crashes through windshield.
June 15, 2004 – Pittsburgh, Pa.
Unwise owl ‘diverts’ incoming flight to Pittsburgh (the plane was taxiing when it struck the bird, damaging its nose gear and causing it to end up off the runway).
Source: USA/Canada Bird Strike Committee