The federal government is moving to protect a group of regular North Shore visitors.
The visitors include the red knot, a robin-sized shorebird known for its 10,000-mile migration from South America to the Arctic.
The Fish and Wildlife Service is proposing that the bird be listed as threatened under the Endangered Species Act. Officials say rising sea levels and disappearing habitat along the East Coast are taking a toll on the rosy-breasted bird, which makes refueling stops on Cape Ann, Cape Cod and Delaware Bay.
While the red knot prefers the sandier beaches of Plum Island off Newburyport, the bird is a regular visitor at Rockport’s Halibut Point State Park on its migration, according to Gloucester resident Chris Leahy, the Gerard A. Bertrand Chair of Natural History and Field Ornithology at Massachusetts Audubon.
Red knot populations have dropped by about 75 percent in Delaware Bay since the 1980s, a result of shrinking habitat and a drastic decline in the region’s horseshoe crab population. Crab eggs are a key part of the birds’ diet, which also includes mussels and clams.
The red knot is already listed as endangered by New Jersey and would join the piping plover as East Coast shorebirds protected under the Endangered Species Act.
Shorebird experts have identified 15 other Atlantic Flyway shorebirds that warrant immediate attention, including the American oyster catcher, lesser yellowlegs, ruddy turnstone and whimbrel.
Leahy said the American oyster catcher has recently returned in larger numbers to the islands of Salem Sound.
Lesser yellowlegs are common on Cape Ann, feeding in the pools of the area’s abundant salt marshes in April and May and again in July through September, Leahy said. Even more common is the ruddy turnstone, which likes to feed among the rocks on the shore in May and September; Leahy says some of these shorebirds winter here, too.