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October 25, 2016
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Twenty years of bald eagles breeding along the Upper Delaware River

A male adult arrives with small mammal remains in its left foot for the pair of three-week-old young looking on in the nest. The silver U.S. Fish and Wildlife Service band on its left foot could not be read over the course of several years when this male was at the nest.

My interest in birds was casual when I was younger, but got a boost in the late ‘70s when I returned to the U.S. from military service and started flying small aircraft over our region's scenic Upper Delaware River Region as a way to unwind.

Aside from the scenic ridges and swift water rapids below, I kept an eye out for birds. In this bird-rich region, what started out as a safety necessity became more and more a quest to identify the rapidly growing dots that quickly appeared as feathers and wings whizzing by at cruising speed.

Birds like vultures and hawks were easily recognizable, but occipiters such as sharp-shinned hawks were smaller and more of a challenge. Geese and waterfowl were present, with flocks easy to spot during migration season. One species was missing though; during my early flights, I saw no bald eagles—no majestic dancers of the sky to share the airspace with.

Eagles, taken for granted by many people today, can be seen throughout the region, and all of our local counties have several occupied bald eagle nests. This wasn't always the case; the effects of DDT caused eagles, as well as several other bird species, to experience reproductive difficulties in the form of thin and brittle eggs that would not endure the incubation process.

In the late 1970s, Pennsylvania was down to three breeding nests and New York was down to a single breeding pair that could not reproduce due to DDT effects, before the chemical was banned. The bald eagle was on the verge of extirpation (local extinction) in NY and PA, and there were no nests within our region.

In 1976, New York State (NYS) initiated a bald eagle reintroduction program where eaglets from Alaska’s plentiful population were placed in cages on man-made elevated nesting platforms called "hacking towers." Eaglets were fed by people who stayed out of view of the birds so the eaglets did not "imprint" on humans as a parent.

At around 12 weeks on, the cages were opened so the eaglets could perch on branches placed on the cages and eventually make their first flight, or fledge. Four years later near Watertown, NY, a pair of these “hacked” eagles was found successfully breeding at a nest of their own. In 1980, the NYS Department of Environmental Conservation (DEC) went large scale with the project, hacking close to 200 eaglets during the next nine years. PA initiated its own reintroduction in 1983.

The Upper Delaware Scenic and Recreational River (UDS&RR), with its 73 miles of river from Hancock to just below Sparrowbush, NY, offers prime habitat, with much undisturbed area, many potential nesting locations and a plentiful uncontaminated source of food for the fish-eating bald eagle. It took close to a decade from the time the first hacked eagles reached breeding age until the first pair of bald eagles established a territory within the Upper Delaware River Area.

Eagles typically establish a nest and take a mate within 50 to 100 miles of their natal nest (where they themselves were raised). The spread of eagles was slow at first, and perhaps some of the area’s earlier territorial eagles may have originated from the Pennsylvania Game Commission’s hacking facility at nearby Shohola Lake in Pike County, PA. The first occupying pair appeared in 1993 along the river, but they did not produce young for the first two years, typical with some newly mated pairs.

The number of bald eagle pairs increased slowly but steadily over the next 20 years to the point that 19 breeding pairs were tallied during the past season in 2013. Nest surveys show that in some cases, the distance between the natal nest and that young's new territory was five miles or less.

Eagles reach breeding age at four to five years, and newly established territories by banded eagles has shown that they tend to get started young; five- to seven-year-old eagles was the norm for banded eagles and a four-year-old female was observed establishing a new territory with an older male (unbanded, but showing four-year sub-adult plumage).

It is impossible to determine the age of eagles by sight once they molt to full adult plumage at five years or so, so banded resightings by birders or photographers are very valuable.

The UDS&RR has proven its worth for bald eagle habitat; even before eagles started to breed here, winter visitors from Canada were utilizing the river for a winter food source while their own breeding habitat was frozen over. For our resident eagles now, the immediate threat is habitat loss. We as a people can work as partners and stewards to minimize this threat.

As I watch an eagle in flight, I stand in awe of nature's perfect airframe. Watching an eagle soar in a thermal, we can see a circle of motion. We are fortunate to live in an area where we are able to observe this winged one's circle of life.