Collision risks rise with bird populations

— -- Populations of large bird species like the one that struck US Airways Flight 1549 last month have grown dramatically in recent decades, prompting aviation experts to warn that the risk of catastrophic collisions with planes is rising.

Successful environmental policies, reductions in hunting and improved bird habitats have allowed the numbers of geese and other large birds to swell, according to the National Audubon Society and government surveys.

"The real concern that I have is that what happened (on the US Airways flight) is really an accident waiting to happen," says Richard Dolbeer, a retired biologist with the Department of Agriculture and an expert in birds' risk to aviation. "We've seen these large increases in population in the bird species such as the Canada goose."

Some possible strategies for tackling the problem, according to Dolbeer and others: reducing bird populations, more rigorous bird controls around airports and better pilot training. Another possibility would be to make existing engines capable of withstanding larger bird impacts — but that's been opposed by the airplane manufacturing industry because it would be costly.

The types of engines that power the A320 and other medium-sized jets were tested only with birds weighing up to 4 pounds. The engines do not have to continue running after ingesting a single 4-pound bird. They must merely stop without exploding or catching fire.

In a 2003 paper, Dolbeer and Paul Eschenfelder, an airline captain who teaches airport wildlife management, identified 36 bird species with average weights above 4 pounds. Three-quarters of the species were growing in population, they found.

From 1990 through 2002, at least 294 planes suffered substantial damage after colliding with birds larger than 4 pounds, they said.

"Our analysis clearly indicated that aviation regulatory and industry groups need to re-examine existing airworthiness standards with regard to bird-strike tolerances," they wrote.