Thursday, December 29, 2016

Bald eagles make Rhode Island comeback

            They’ve been observed eating Canada geese on highway medians, soaring over shopping center parking lots, perched in trees in bustling Providence, and hunting for fish at nearly every large unfrozen lake in the state. All of which suggests that sightings of bald eagles in the Ocean State are no longer the rare occurrence that they used to be. In winter, they have become almost commonplace.
Last January alone, bird watchers reported seeing bald eagles at Brickyard Pond in Barrington, Watchaug Pond in Charlestown, Tiogue Lake in Coventry, Stump Pond in Smithfield, Trustom Pond and the Great Swamp in South Kingstown, the Pawcatuck River in Westerly, and flying over numerous other locations.  As many as nine bald eagles were sighted together on the Seekonk River, which is now considered the most reliable place to find the birds in Rhode Island.
Bald eagle photo by Peter Green/Providence Raptors

And experts say that eagle numbers are expected to climb even higher.
According to Tom French, the assistant director of the Natural Heritage and Endangered Species Program for the Massachusetts Division of Fisheries and Wildlife, who has been monitoring bald eagle numbers in New England for more than two decades, many of the eagles sighted in Rhode Island in winter are year-round residents, but they are less noticeable during the breeding season.
He said that Rhode Island has four nesting pairs of eagles, and most of their young probably stick around the area for a few years before dispersing to find breeding territories of their own.
“At our latitude, most adult eagles don’t migrate,” French said. “Rhode Island also gets some spillover in the winter of eagles from Massachusetts and Connecticut.
“Plus we have a contingent of eagles from Maine and southern Canada that migrate. How far they go is questionable – some definitely go as far as Chesapeake Bay – but many of them only go as far as they have to to find open water,” he added. “So some of them probably stop along the Rhode Island coast.”
How many bald eagles spend the winter in Rhode Island is difficult to say, since some of the birds move around when ponds and lakes freeze.
“The number you have in winter is not only based on increases from breeding, but also based on the weather,” French said. “A good winter for eagles in Rhode Island means it’s probably been a bad winter weather-wise elsewhere. The colder the winter in the north, the more eagles you’ll have in Rhode Island.”
That’s what may account for the dearth of bald eagle observations in Rhode Island so far this winter. Rachel Farrell, a member of the Rhode Island Avian Records Committee, said that reported eagle observations in December have been about half of what they were last year.
“Perhaps the eagles have stayed to the north so far this winter,” she said. “We may see a huge number of reports in January, which is often the case.”
Rhode Island hasn’t always had significant numbers of eagles in winter, however. Farrell said that bald eagles were fairly common winter residents in Rhode Island up until the 1960s, after which they nearly disappeared from the state for 30 years. Only two bald eagles were observed during the annual Christmas Bird Counts between 1962 and 1988.
The decline, according to both Farrell and French, was caused by the use of the pesticide DDT, which made its way into lakes and ponds and accumulated in the tissues of fish. When eagles ate the fish, the toxin caused reproductive failure, resulting in a precipitous decline of bald eagle populations throughout the Lower 48 states.
            DDT was banned in 1972, but it has taken a surprisingly long time for the birds to rebound. Ospreys, the fish-eating hawks that are now common throughout the region, were similarly affected by DDT, but they recovered their populations much more quickly than have bald eagles. It took many years of work by wildlife officials, including Tom French, to relocate eagle chicks from other parts of the country and place them with “foster parents” at the Quabbin Reservoir in Massachusetts before the New England eagle population began to grow on its own.
            French said that bald eagles have now recovered in the region and are still experiencing exponential growth. Eventually that population growth will level off, when the birds are so abundant that there is no longer enough nesting habitat or food resources to sustain them.
            “But they haven’t even begun to level off yet,” he said.
            Is there a downside to having so many eagles in the region? That’s a question that Peter Paton has pondered. An ornithologist and professor at the University of Rhode Island, Paton said that researchers have found that the approximately 900 pairs of bald eagles breeding in Maine are eating so many gulls, eiders and great cormorants that populations of those birds are declining. And many of the eiders and cormorants that summer in Maine spend their winter in coastal southern New England. Which means that eagle predation in Maine may be causing a decline in winter eider and cormorant numbers in Rhode Island.
            French, who assesses eagle prey whenever he visits a nest to band young eaglets, said that the most common food items he observes in nests are fish, primarily brown bullhead and chain pickerel. But he also commonly finds the remains of Canada geese, wild turkeys, gray squirrels and other prey.
            “Most of what they eat aren’t things we really need to worry about,” he said. “Sure, they’ll take a few things that you wish they hadn’t, like common loons and osprey chicks, but they won’t impact other species at the population level.
“For all practical purposes in Rhode Island,” French concluded, “there’s no such thing as too many eagles.”

This article first appeared in on December 29, 2016.

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