Bald Eagles and the C&O Canal National Historical Park
The Bald Eagle, once listed for nearly 30 years as a federally endangered species by the U.S. Fish and Wildlife Service, is now listed as threatened. Bald Eagle populations plummeted in the 1960s and '70s due to effects of the pesticide DDT, habitat destruction, and lead poisoning from eating hunter-shot waterfowl containing lead shot. By the mid-70s, fewer than 500 pairs of Bald Eagles remained in the lower 48 states. About 300 of those were in Florida; about 70 pairs were in the Chesapeake Bay area. Maryland Department of Natural Resources (DNR) documented 41 pairs in the state's first aerial count in 1977.
DDT was banned from use in the U.S. in 1972 and the use of lead shot was finally phased out in 1991. Since then, the species has steadily recovered to the point it could be reclassified. Reclassifying a species from endangered to threatened status means the species has not fully recovered, but is no longer in immediate danger of extinction.
Recent population estimates show there are about 40,000 Bald Eagles in Alaska and about 4,500 nesting pairs in the lower 48 states. In Maryland, the number of nesting pairs of Bald Eagles has steadily risen topping 300 in 2001 with 315 pairs documented by the Maryland DNR.
Bald Eagles have nested on Conn Island in the Potomac River, near Potomac, Maryland since 1986. That year the pair were probably a first year breeding pair (about 5 years old). Eagles are known to form long-term bonds, so it is probable this is the same pair that has returned every year since then to nest here. In 1988, the eggs failed and the nest tree fell over. When the pair returned in 1989, they built a replacement nest in the tree presently used and fledged two young.
Conn Island was donated to the Nature Conservancy (TNC) by PEPCO in 1997. TNC, a non-profit organization, plans to donate the island to the C&O Canal National Historical Park in the near future. It will then be incorporated into the park's official boundary.
The Conn Island Bald Eagle nest is one of the few eagle nests in Maryland located on non-tidal water. Most are located on tidal water where their main food supply, fish, is more stable. Conn Island is also one of the furthest west of all documented active Bald Eagle nest sites in Maryland.
Adult Bald Eagles are 3' or more in length head to tail with a 6-7 1/2' wing span and weigh around 10 pounds. Females are larger than males. Both sexes are very large, dark brown-colored birds with a distinctive white head and tail. Immature birds are dark brown all over and somewhat mottled, not attaining adult plumage until reaching maturity around 4-5 years of age. Balds may live 30 years or more in the wild, possibly longer in captivity. They build massive stick nests in the tops of trees that are reused year after year. Some nests may reach as much as 10 feet across and weigh between 1,000-5,000 pounds!
Similar species such as Osprey, Turkey Vultures, and Black Vultures are often confused with Bald Eagles in the field:
Lucky for us! The Conn Island birds and their nest can be viewed with relative ease and little disturbance to the birds from the Washington Aqueduct Observation Deck located near Great Falls Tavern Visitor Center, C&O Canal National Historical Park, Potomac, Maryland. Use a spotting scope to view inside the nest or basic binoculars to view the birds at a distance. Sometimes the birds fly right overhead. Who needs binoculars!
The birds can see activity on the observation deck, but are far enough away that they seem to tolerate it. People, boats, and helicopters can cause eagles to abandon nest sites if the disturbance is too close for too long. The critical time for the birds is January 1 - June 15. During this period courtship, mating, nest building, egg laying and incubation occur. After this critical period, the young are almost ready to be on their own.
The Natural History of Bald Eagles
The Bald Eagle's diet consists primarily of fish. Eagles catch fish in their talons as the fish swim near the surface. Bald Eagles are notorious for pirating, or stealing, fish from other birds, but this behavior is less prevalent than once thought. They will also eat small mammals such as muskrats, squirrels, rabbits, and other birds such as ducks, coots, mergansers, and even gulls.
Bald Eagles live along seacoasts, lakes, rivers and marches. Their breeding range spans from northern Alaska through Canada and the Great Lakes region and includes the east and west coasts of the U.S. Their winter range spans throughout the lower 48 states down to northern mexico, especially along major river systems of the interior U.S.
The Bald Eagle's courtship begins in December or January. Nest Building and spectacular aerial courtship displays are good indications that a pair will soon nest. Typically, 2-3 eggs are laid in February and hatch in late March; both parents share in the incubation of the eggs and feeding of the young. It is not uncommon for nests to fail due to severe weather, predation, and other factors. The young begin flight in June and will stay in the area until September, when they leave permanently.
A Stewardship Message
The recovery of the Bald Eagle is an Endangered Species Act (ESA) success story. Other species such as Peregrine Falcons, have or may soon follow suit. however, it must be said that DDT is still used in other countries and Kelthane, another pesticide containing small amounts of DDT, is still legal in the U.S.
Additionally, habitat loss is a continuing threat to the recovery and survival of Bald Eagles and other wildlife species. The ESA and other laws that protect wildlife are essential for preserving our natural heritage.
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Did You Know?
Transporting goods and people by canal dates back to antiquity. The lock gates used on the C&O Canal were an adaptation of a design by Leonardo DaVinci in the late 1400's. Until the advent of the railroad, water travel was far superior to land travel.