Birds fly into airplanes every day, and most do so without causing major damage.
It usually doesn't even register as turbulence, said John Ostrom, who chairs the Bird Strike Committee USA, formed in 1991 to analyze bird strike data and advise the aviation industry.
But bird strikes can be deadly, with more than 200 people killed since 1988 because of airborn collisions with birds, according to Ostrom's committee.
By a relatively rare fluke, a pair of bird strikes apparently disabled a US Airways jet today, sending it splashing into the icy Hudson River. All 150-plus passengers were reportedly safe after a quick rescue effort.
"There's a variety of ways a bird can take down an airplane," said Ostrom.
Birds can disable planes, Ostrom said, by flying into the engines and shutting them down. They can also penetrate the windshield or other parts of the fuselage, causing pilots to lose control.
And apparently when it comes to collisions with birds, size doesn't always matter.
"There have been instances where birds the size of robins bring a plane down, all the way up to Canada geese," Ostrom said, adding that a bird simply smacking into the side of a plane will not cause it to crash.
Even when birds don't cause death, injury or drama like today's Hudson River rescue, they do cost airplane owners money.
The Federal Aviation Administration's Web site on Airport Wildlife Mitigation says that bird strikes do more than $300 million of damage each year.
While there are wildlife mitigation options for airports, there's not much a pilot can do to avoid birds in the air.
"You're not going to move the airplane like you're moving a car or moving a bike," he said. "When you're moving something at 100 mph, it's pretty much straight on."
Veteran pilot William Givens of Roanoke, Texas, said he usually never even knew he hit birds until he saw the damage when he landed.
Givens, who flew planes for the Air Force in Vietnam and later for Delta, said the threat bird strikes were part of life as a pilot. But it's a silent danger.
"You don't notice," he told ABCNews.com. "You just see the damage after the flight."
Birds usually don't fly any higher than 5,000 feetr, he said, and the policy to stay under 250 knots, or about 290 mph, under 10,000 feet also helps minimize damage from the larger birds.
"Still," he said, "hitting a goose at 250 knots -- it's going to do something."
The FAA's Web site on wildlife mitigation cites several factors as to why birds and other animals have become a growing problem for the airline industry.
Jet travel has become less noisy and done away with the slower piston-powered planes and there are many more planes in the air between private, commercial and military aircraft. Many modern airports, the Web site noted, are surrounded by natural habitats that draw in birds and, as a result, most bird strikes occur near the airports.
To that end there are things airports can and are doing to reduce the chances of bird strikes, Ostrom said.
Some airports have chosen to make modifications to surrounding habitat to discourage birds from nesting. Others have taken to using dogs and other measures to scare the birds away and some have resorted to "lethal control," or killing nuisance birds, he said.
Andrew Maloney, an attorney and partner with Kreindler & Kreindler LLP in Manhattan, said the US Airways crash will very likely have a major impact on ongoing discussions about the bird problem at New York's LaGuardia Airport, where the plane took off today.
Maloney, whose firm specializes in aviation issues, said city and Port Authority officials want to clear the area surrounding LaGuardia Airport of birds, but environmentalists don't want the birds, mostly seagulls and Canada geese, disturbed from their nesting grounds.
LaGuardia, he said, was built on swampland and the main runway is just hundreds of yards away from Riker's Island, which with its grassy areas, trees and water access is prime nesting ground for birds.
Maloney said his firm was contacted by the city last year about working on a panel to resolve these issues, but the notion petered out and nothing was ever organized.
"This is the exact scenario the panel was supposed to address and discuss," he said.
The Bird Strike Committee's Web site reports that about 90 percent of all birds involved in airplane collisions in the United States are species that are protected by the federal Migratory Bird Treaty Act.
The most recent bird strike that took down a plane in the U.S. was in October 2007, when an instructor and student died in a crash into a bog en route to Grand Forks, S.D. from Minneapolis. Remains of a Canada goose were found in the plane wing and the horizontal stabilizer was damaged.
On Nov. 10, a pilot of a Ryanair flight was forced to make an emergency landing in Rome after multiple bird strikes killed both engines. Three passengers and two crew members were injured.
The first recorded bird strike, according to the Bird Strike Committee's Web site, was in 1905, when Orville Wright's plane hit a bird and killed it.
Birds aren't the only animals that cause damage to planes. The Bird Strike Committee reported more than 760 collisions with deer and more than 250 with coyotes between 1990 and 2007.