Peregrine's Commonwealth Comeback Continues

Use of more cliffs would complete this bird's marvelous recovery

HARRISBURG, Pa., Aug. 20 /PRNewswire-USNewswire/ -- The peregrine falcon has firmly reestablished itself in the Commonwealth 50 years after its near extinction. But the Pennsylvania Game Commission wants more from peregrines before it will remove them from the state endangered species list.

"The peregrine falcon's ongoing comeback and expanding nesting range have sparked considerable excitement throughout Pennsylvania, from our quietest rural areas to our largest cities," said Game Commission Executive Director Carl G. Roe. "There are 29 active peregrine nests in 14 counties and they have drawn great interest. They truly are an attractive, charismatic species and their recovery from the brink of extinction has everyone pulling for them.

"However, peregrines need to occupy more of their historic nesting sites before we can remove them from the state endangered species list," Roe explained. "This year's 29 nests are great news when you compare them to the 40 or more sites they used annually in the early 1900s, because it represents substantial progress. But only four of the 2010 nests are on cliffs, which was where almost all of their nests were located prior to their dramatic decline after World War II. So we're looking for peregrines to occupy more river bluffs and precipices. Then we'll relax a little more."

It's not that the Game Commission considers the preponderance of peregrine nests on building ledges and bridges to be inconsequential in the big picture. Just that biologists believe lasting peregrine population stability is directly related to reclaiming the cliffs where they're less susceptible to the unique mortalities associated with living on manmade structures directly over large rivers and above cities.

Back in 1964, as America was reaching into space with Gemini, the peregrine falcon finally lost its grip on what remained of its fading existence in the eastern United States. That year, extensive fieldwork throughout the eastern United States – which once supported an estimated 350-400 nesting pairs of peregrines – failed to turn up one occupied nesting territory. The fastest animal on Earth was gone east of the Mississippi to the Atlantic. In 1975, North America's population was 324 nesting pairs, which was 80-90 percent below historical levels.

DDT was the biggest problem peregrines and many other birds – from bluebirds to bald eagles – faced. Its widespread use began shortly after World War II and continued into the mid 1960s. DDE, a metabolite of the pesticide, bioaccumulated in a bird's body from eating contaminated prey and induced it to lay calcium-deficient, thin-shelled eggs that broke when sat upon. As North America's peregrine population continued to collapse, and Rachel Carson helped America understand how that was happening, it became clear that DDT and other organochlorine pesticides had to go. They were banned in the United States in 1972.

The Peregrine Fund and the U.S. Fish & Wildlife Service didn't wait long to start a recovery. They began releasing captive-bred peregrines into the wild in 1974 and continued for 14 years. Releases occurred throughout the continent, including in Pennsylvania and neighboring states. In 1980, captive-bred peregrines nested successfully for the first time in New Jersey. Pennsylvania found its first three peregrine nests in the late 1980s on large bridges near Philadelphia and Chester. Since then, the species has reestablished its presence slowly in Pennsylvania and elsewhere, and continues to push into new areas of the state annually. The continental population of peregrines currently numbers more than 3,000 nesting pairs. They were removed from the federal endangered species list in 1999.

Twenty-three of the 29 known active nests in Pennsylvania successfully fledged young peregrines this year. The number of total active nests and 23 nests fledging young are both records for Pennsylvania's ongoing recovery period. This year, 62 young falcons have fledged. A record 68 peregrines fledged from Pennsylvania nests in 2009.

"The peregrine's comeback in Pennsylvania is substantial, regardless of how you examine it," explained Dr. Art McMorris, coordinator of the Game Commission's peregrine management program in recent years. "The data show they have firmly reestablished their population and their recruitment is phenomenal. But we still are sorely lacking in cliff recolonization. The reasons for this are undoubtedly complex, and not totally understood. But they may be related to predation and competition for nesting areas from great horned owls, overgrown vegetation on historic nesting ledges, and attractions in urban areas, such as the abundance of prey species."

The peregrine's great horned owl problems and proclivity for using manmade structures certainly seem related. Early attempts to release captive-bred peregrine chicks from historic Pennsylvania nesting sites were thwarted by great-horns, which killed the young peregrines. As peregrines began to nest on the bridges near Philadelphia and Chester, biologists took note. Many of these birds came from nest towers built to reintroduce them, and it's possible they looked for similar structures when they became nesting adults. Biologists also believe peregrines are fond of urban skylines because they rarely harbor great horned owls.

"Peregrines did nest in or adjacent to areas with great horned owls in Pennsylvania's past," McMorris said. "And there's no doubt that a pair of adult peregrines can compel a great horned owl to steer clear of its nesting scrape. But young peregrines are no match for great horned owls. That's why those early releases didn't work. Eventually, peregrines found a way around the owls, and it's that same intuition that will help them reclaim those historic cliffs. I'm confident that they'll get there."    

This year, 54 young were banded in Pennsylvania, two as late as July 13. The latecomers were from a nest in Columbia, Lancaster County; the pair started nesting four years ago and finally succeeded this spring. A breakdown of young banded by county is as follows: Allegheny, 13; Philadelphia, 7; Luzerne, 5; Berks, 4; Clinton, 4; Dauphin, 4; Bucks, 3; Delaware, 3; Lancaster, 2; Lehigh, 2;  Montour, 2; Northampton, 2; Lycoming, 1; and York, 2.

Three times this past spring, the state Department of Transportation has helped Game Commission employees access peregrine nests on bridges crossing major rivers. On the Interstate 81 bridge north of Harrisburg, William Huehn, a PennDOT crane operator, found a nest with eggs during a routine inspection. PennDOT immediately shut down operations near the nest until it could lower on the crane Dan Brauning, Game Commission Wildlife Diversity Program chief, to inspect the nest site. Later the nest was found to be abandoned; two of the three eggs were missing. The third never hatched.

PennDOT also provided crane assistance to Brauning at the McElhattan Bridge in Clinton County to band four young peregrines. PennDOT also lowered Allegheny County Wildlife Conservation Officer  Beth Fife on a crane to a nest under the Westinghouse Bridge in Pittsburgh, where she banded three youngsters, all males.

Other partners who provided cranes and crews to operate them this spring were the Delaware River Joint Toll Bridge Commission on the Scudder Falls Bridge in Yardley, Delaware County, and the PPL Corporation for the Eighth Street Bridge in Allentown, Lehigh County.

At the Route 322 bridge over the Susquehanna River at Clark's Ferry, Perry County WCOs Steve Hower and Jim Brown and biologists Brauning and McMorris combined efforts to confirm a new nest. WCO Hower and McMorris both later verified there were three young falcons, they were too old to band and that one had fledged.

Peregrines aggressively defend their nest sites. In fact, it's rare when peregrines abandon an established nest. "Once peregrines are successful at a site, they are very site-faithful," McMorris said.

One pair that puts up with a lot and continues to hold on to its nesting claim is the pair on the 15th floor of the Rachel Carson Building in Harrisburg. The 12-year-old female there is the oldest currently nesting in-state. It's a distinction she received only recently.

The Harrisburg female has been a belligerent bird intolerant of ledge visitors for years. Each year, her rage seems to exceed the previous year's steely performance at banding time. Despite the intrusions, she stays on. There's little doubt she'll go down fighting before ever being pushed away.

The state's former falcon matriarch – a 14-year-old female – on the Gulf Tower was deposed by a younger female after she laid two eggs in the scrape this spring. Her mate stayed on with the new female, and then more drama ensued on the 37th floor ledge.

"It took about two weeks for the new female to hormonally and physiologically get into breeding condition," explained McMorris. "In the meantime, the two eggs just sat there. She kept pushing them away and he kept pushing them back. The eggs even got snowed on. We never expected them to hatch. About two weeks after she arrived, the new female laid three more eggs and then hatched all five! Better yet, all five fledged. Wow!"

The Gulf Tower nest has been Pennsylvania's most productive nest over the past two decades. Since 1991, it has fledged an amazing 68 peregrines.

Peregrine falcons are undoubtedly one of the bird world's most fascinating members. But during their heyday in the early 1900s, few Pennsylvanians knew of them. There really weren't that many of them. To birders, they were a must-see species. But others saw them differently, as "duck hawks" and "chicken thieves." In addition to its perception problems, the peregrine falcon really didn't receive any type of protection from the early 1900s until they were protected – along with other birds of prey – by an amendment to the Migratory Bird Treaty with Mexico in 1972. Prior to their population's collapse after World War II, peregrine nests were raided for eggs and young.  

Today, their reputation is more complimentary, countless Pennsylvanians are interested in their exploits, and their future is brighter than it has been in half a century. American painter and turn-of-the-century birder Gerald H. Thayer saw a century ago what many people are just coming to learn today about peregrines.

"The peregrine falcon," wrote Thayer in a 1904 edition of Bird Lore, "is, perhaps, the most highly specialized and superlatively well developed flying organism on our planet today, combining in a marvelous degree the highest powers of speed and aerial adroitness with massive, warlike strength."

To learn more about this Pennsylvania endangered species and others, visit the Game Commission's website at www.pgc.state.pa.us and select "Endangered Species."  

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NOTE: A photograph to accompany this news release is available from the Game Commission's website (www.pgc.state.pa.us) by clicking on "Resources," then choosing "News Releases" and then selecting "Release #085-10."

SOURCE Pennsylvania Game Commission