HACKENSACK, N.J. - A rare songbird that uses North Jersey forests during migration has suffered such a decline in numbers that federal officials say it may land on the endangered species list.
The concern about Bicknell’s thrush triggers formal review by the U.S. Fish and Wildlife Service.
Bicknell’s thrush, related to the robin, breeds in stunted spruce-fir forests at high elevations from the Catskills region in New York state through Maine and into Canada. It is one of the rarest birds in North America, and it migrates through New Jersey every spring and fall between those breeding areas and wintering grounds on major Caribbean islands.
The bird, less than 7 inches long and weighing about an ounce, has steeply declined in its Canadian population because of habitat loss from human activity. It also has lost habitat at its wintering grounds to logging and farms.
The Fish and Wildlife Service review was sparked by a petition by the Vermont-based Center for Biological Diversity. Scientists already have documented 7 to 19 percent annual declines in parts of the bird’s range, the center reports.
Researchers especially worry that climate change could raise temperatures enough to force high-elevation forests of its breeding areas to retreat farther north, eliminating these birds completely from the northeastern U.S. Also, the earlier onset of spring weather could cause the thrush’s food supply - insects - to peak before the birds ever get to breeding sites, hastening their demise.
“Climate change will have disproportionate impacts on species that live at high elevations,” Noah Greenwald, the center’s endangered species program director, said when the petition was filed. Bicknell’s thrush, he said, is “literally going to be pushed off the top of the mountain.”
Rising temperatures also tend to increase spruce and fir cone crops in the high-elevation forests, and the cones are a key food source for red squirrels, which also prey on the thrushes’ eggs and young.
“This year is the warmest on record in the Northeast, so the need to protect the Bicknell’s thrush couldn’t be more urgent,” said Mollie Matteson, a conservation advocate at the center.
The birds live about two years. During their spring and fall migrations they keep to a narrow band between the coast and the Appalachians, making New Jersey a vital stopover to refuel.
“I have seen this bird several times in New Jersey,” said Pete Bacinski, director of New Jersey Audubon’s Sandy Hook Bird Observatory. “This bird definitely deserves federal listing, since the numbers continue to decline.”
The best spots to see the bird locally are Garret Mountain Reservation in Woodland Park and in Mahwah’s Ramapo Mountains and along the Palisades, said Bacinski and Michael Newhouse, a naturalist and bird researcher with the Meadowlands Commission.
But the Bicknell thrush is hard to identify: It closely resembles the gray-cheeked thrush. Bicknell’s thrush has olive-brown upper parts, white belly and spotted breast, and some chestnut color on its wings and tail.
“I have never been fortunate enough to see one myself,” said Don Torino, president of the Bergen County Audubon Society. “All thrush habitat in general needs to be protected in New Jersey, to protect declining species such as the wood thrush and gray-cheeked thrush.”
A listed species receives protections including restrictions on harming, disturbing or killing it, a requirement that federal agencies develop a recovery plan to aid resurgence, and the availability of federal funds to help buy land or exchange it to protect habitat.
The focus is on protecting breeding grounds, Newhouse said, but even a state in the migratory path could be affected.
“Since Bicknell’s thrush migrates through New Jersey, impacts would be related to activities that affect migration,” said Fish and Wildlife spokeswoman Meagan Racey. “That could include, for example, wind turbines that are in the migration corridor.”
The federal endangered species list already includes two bird species in New Jersey: the piping plover and the roseate tern.