Tuesday, March 15, 2016

Treehugger Tuesday

Published in the Alaska Dispatch News:

Bald Eagles Growing Increasingly Comfortable with City Living
Gregory Lee Sullivan
March 13, 2016


A bald eagle perched in a tall tree along Fones Cliffs in Singerly, VA on July 14, 2015. The area is home to a large population of eagles; the cliffs make a perfect perch for hunting and nesting.

If there's a time of year to see a bald eagle, this is it. But those who spot one during the current nesting season won't be observing quite the same national bird as in decades past.

"The main thing is they just don't really care as much about people anymore" and now can be found nesting in residential areas, said Kevin McGowan of the Cornell Lab of Ornithology, based in Ithaca, N.Y.

According to scientists, changes in the behavior of the bald eagle - from a bird once found only deep in the wild to one willing to cohabitate with humans - are the result of laws that protect the bird and have helped the species recover after nearly dying out in the early 1960s. The government is empowered to go after those responsible for the death of bald eagles - even if it's unintentional (such as in the case of a New York farmer who received a fine and probation last year after several eagles died from poisoned meat he had set out to kill coyotes). Federal and state officials are investigating what happened to 13 bald eagles found dead recently near a farm on Maryland's Eastern Shore.

Bald eagles "are coming in on their own and putting their nests in people's front yards, and in parks and in gardens and things like that. That just didn't happen in the '60s and '70s," McGowan said. "They'd pick a big tree that was way the heck away from all the people."

While bald eagles are still rare in large cities, researchers have documented eagle nests recently not just in the Washington area, which boasts the largest numbers on the East Coast, but also in New York - where in 2015 the first nesting pair was spotted in more than 100 years - Philadelphia, Pittsburgh and Miami, where a pair built a nest atop a cellphone tower.

The bald eagle's historical range covers most of North America. The bird was hunted for sport before the Bald Eagle Protection Act of 1940 outlawed the practice; that ban was reinforced by the Bald and Golden Eagle Protection Act in 1962. The pesticide DDT was found to cause eagle and other species significant difficulties with reproduction. By 1963 America's iconic bird was on the verge of dying out in the nation's 48 contiguous states. But with the banning of DDT in 1972,combined with more federal and state protection and recovery efforts, the species has made a steady rise.

The number of breeding pairs in the 48 contiguous states increased from a low of 487 in 1963 to 9,789 in 2006, according to data from the U.S. Fish and Wildlife Service, which removed the species from the endangered list in 2007.

While that federal agency no longer publishes regular national figures on the bird's status, Bryan Watts, director of the Center for Conservation Biology at the College of William and Mary in Williamsburg, Va., said that a conservative estimate would put the number of pairs in the Lower 48 states today at around 24,000. Watts said that the Chesapeake Bay region has the largest bald eagle population along the Atlantic Coast, with about 2,000 nesting pairs, although Florida also has a large population.

Other areas with large numbers of bald eagles include Alaska (where the bird was never threatened), the Great Lakes, the Pacific Northwest and the Yellowstone area.

Every winter, Watts and a small team of researchers estimate the bald eagle's Chesapeake Bay population, using a small airplane to survey established nests.

The species's growth, particularly on the bay, has been remarkable, he said. "If you go back to the 1980s and early 1990s, we had virtually no eagles in urban areas," he said, "and our perception of eagles was that they needed fairly remote places away from humans - and they probably did at that time."

But now, researchers say, as eagle populations have expanded and the birds may no longer consider humans to be predators, suburbs and urban areas near waterways provide attractive nesting areas. In the Washington area, it's not just the Chesapeake Bay that provides a good home; in recent years nests have been seen near Ronald Reagan National Airport and the Beltway, and recently one couple has made a home at the National Arboretum in Northeast Washington.

In New Jersey, scientists reported only one active bald eagle nest in 1982 - in the middle of a remote swamp.

"We had this now naive idea that this is what eagles in New Jersey needed, so we were thinking, where else are these great forests?" said Kathleen Clark, leader of the state's eagle project, which released 60 young birds between 1983 and 1991. "But nest number 2 was on the edge of a farm field," she said. "With nests 2, 3 and 4, we started seeing they were keying into where there was food and not exclusively large tracts of forests." New Jersey's efforts have resulted in the establishment of 161 nests today, many in densely populated suburbs close to New York City.

Clark and other eagle researchers said it would be a mistake to assume that all bald eagles have become tolerant of people; in fact, many shy away from human activity, and the Fish & Wildlife Service recommends keeping away from nests to avoid disturbing them.

Watts, meanwhile, said the growing number of eagles has meant that he and his team have been able to observe aspects of eagle behavior that weren't evident in the past.

"It used to be, when I started flying in the early '90s, you rarely would see birds that were guarding" against intrusions by other eagles, he said. Now, there is real competition for prime nesting locations on the Chesapeake. He has been observing more and more fights within the population, and more of the birds are being admitted to rehab centers for injuries.

Watts said the birds spend less time foraging, which causes an increase in the adult mortality rate, bringing population stability. Stable numbers, he said, are a sign that the bald eagle community has reached a healthy point.

Watts and Clark said the growing Chesapeake Bay eagle population has helped increase numbers in nearby states as the birds move there to set up nests.

McGowan said he realized that bald eagles had begun to adjust to humans when he came across a nest in Virginia's Norfolk Botanical Garden a few years ago.

"You could walk right up to it, and it's in the middle of the . . . [garden] with sidewalks all around it," McGowan said. "This is not a scared wild bird that we have to worry about disturbing a nest. Here it is, right in the middle of fairly heavy traffic."

The nest proved to be a little too close to humanity, though. One of the eagles using that nest was killed after it was hit by a plane at a nearby airport. The nest was relocated to a more placid spot.

While it's still nesting season, McGowan said he encourages people to get out of their warm houses with a pair of binoculars and catch a glimpse of an eagle for themselves.

"They have a wingspan bigger than your arms. They have toes about the same size as your fingers, only they've got giant claws on them. You don't have to be a birder to appreciate a bald eagle. They're an impressive freaking animal."

But don't get too close, he said. "There are inevitably going to be human-wildlife conflicts as wildlife comes back," McGowan said. "But to me, what a good problem to have."

The return of the bald eagle is "arguably one of the greatest success stories that our nation has seen," Watts said. "It's a really rare situation where we as a culture can say that we changed the trajectory of an entire species. That's what happened."

No comments:

Exploring urban nature, birds, birdwatching, birding, hummingbirds, butterflies, dragonflies, bees, hawks, raptors, wildflowers, trees, mushrooms, environment, binoculars, spotting scope