Note to Ospreys: Bald Eagles May Be Moving Into the Neighborhood

Three-year-old juvenile bald eagle flies over Fishers Island, Jan. 20, 2021. John Spofford Photo

Reports of bald eagle sightings have filtered through the Fishers Island community for the past three years. It makes sense, since there are four times as many bald eagles in the lower 48 states than there were a decade ago.

The U.S. Fish and Wildlife Service (USFWS) in March reported 316,708 bald eagles in the lower 48. The 71,467 nesting pairs observed are double the number in 2009 and a stark contrast to the all-time recorded low of 417 known bald eagle nests in 1963.

On Fishers Island in the 1960s and early 1970s, before DDT (banned in 1972) had nearly decimated osprey and bald eagle populations, the only osprey nest observed on Fishers Island was near Airport Road. In 2018, Andrew Edwards used a drone to count 17 active osprey nests and 34 fledglings on Fishers Island.

If bald eagles start nesting on Fishers Island, they will be looking for food. They eat birds, reptiles, amphibians, rabbits and muskrat (both live or as carrion). But they also love fish, which comprise 99 percent of the osprey’s diet.

Ospreys and opportunistic bald eagles share much of the same habitat, and ospreys are often on the losing end. Rather than doing their own hunting, bald eagles will sometimes harass ospreys, stealing fish directly from their talons or making them drop fish they’ve just caught, grabbing the fish in midair. Bald eagles are also known to raid osprey nests and snatch fledglings, whether small or just ready to fly.

Ospreys do their best to stand up to the brute force of bald eagles by buzzing them in the sky and sometimes attacking them on the ground.

Using citizen science to help count bald eagles and nesting pairs, USFWS Migratory Birds Program integrated data from its aerial surveys with data collected from observations by 180,000 birders, which had been collated by the Cornell Lab of Ornithology.

The bald eagle (l) is one of the largest birds in North America, with an average 80-inch wingspan and weighing 6.5 to nearly 14 pounds. Osprey (r) have an average 59- to 70-inch wingspan and weigh 3-4 pounds. They have long, narrow wings with a marked kink (not as apparent in this image) that makes them look like an M-shape from below.