If you happen to see a bald eagle soaring above the Wissahickon, it is not a mirage. Bald eagles have, in fact, been spotted in the area.

by Brenda Malinics

Sheepishly, my friend shared the news that she thought she had seen an eagle on her morning walk in the Wissahickon. “That's not possible, is it?” she asked. It's possible, I assured her; indeed, the eagle has landed in Philadelphia.

The first bald eagle nest in Philadelphia in modern times was discovered around 2007 at the Navy Yard. It was later abandoned, but eagles took up residence at the Heinz National Wildlife Refuge in Tinicum, in Pennypack Park and now in the Wissahickon.

There are two active eagles’ nests in Philadelphia. The exact locations of nests are always a closely guarded secret among birders, and I'm not giving it away.

The bald eagle is truly one of America's success stories. In the 1960s, there were fewer than 450 nesting pairs in the Lower 48. Their population had declined from an estimated 100,000 pairs in the late 1700s.

There are now more than 4,000 adult bald eagle nesting pairs and an unknown number of young and sub-adults in the U.S. The Pennsylvania Game Commission reports more than 254 active eagles nests in the state. Eagles are still listed as “threatened,” but they were recently removed from the federal Endangered Species List.

Many feared that bald eagles would become extinct due to habitat destruction, illegal shooting and the havoc wreaked by DDT. Eating fish contaminated by this once widely used agricultural pesticide caused eagles to lay eggs with shells so thin that the weight of the parent crushed them during incubation.

DDT was banned in the U.S. in 1972, however, in large part due to Rachel Carson's famous book “Silent Spring.” (Unfortunately, it is still used in other parts of the world, with the same negative consequences for fish-eating birds.) The ban and an aggressive reintroduction program worked to bring the bald eagle back from the brink of extinction.

Male bald eagles measure 3 feet from head to tail, weigh 7 to 10 pounds and have a wingspan of about 6½ feet. Females are even larger, some reaching 14 pounds and having a wingspan of up to 8 feet. This raptor has large, pale eyes, a powerful yellow beak; and great, black talons. The distinctive white head and tail feathers appear only after the bird is 4 to 5 years old.

Eagles can live 30 years in the wild, and even longer in captivity. They mate for life and build huge nests in the tops of large trees near rivers, lakes and marshes. Nests are often reused year after year; some may reach 10 feet across and weigh as much as a ton.

Although eagles may range over great distances, they usually return to nest within 100 miles of where they were raised. Normally, they lay two to three eggs that hatch in about 35 days. The eaglets can fly within three months and are on their own about a month later. But only about half survive their first year due to poor hunting practices, bad weather or human interference.

The staple of most bald-eagle diets is fish, but they will feed on almost anything they can catch, including ducks, rodents, snakes and carrion. Because Philadelphia is located along major waterways, there is an abundance of food for eagles year-round.

Bald eagles have few natural enemies, but the presence of humans continues to negatively impact their habitat and future. Still, this majestic bird is increasing and showing up where it is least expected.

Bald eagles less than 5 years old are mottled brown all over. In addition to their impressive size, eagles don't flap much and soar with straight wings. Birders refer to them as “flying boards.” So be on the lookout for bald eagles in the Wissahickon and be prepared to be awed.

Brenda Malinics, of upper Roxborough, is a wildlife expert, a nationally recognized authority on bats, a prodigious cat rescuer and the founder of Brenda’s Cat Rescue, a non-profit organization that has found good homes for countless rescued cats and kittens. More information at bmalinics@gmail.com or www.brendascatrescue.com.