Albany, N.Y. ? States from Maryland to New York have joined in an uncommon effort to help a struggling bird’s 8,000-mile migration from the tip of Argentina well into Canada.

Every spring, the 5-ounce red knot travels from South America, feasting on horseshoe crab eggs in the Chesapeake Bay before taking on the last leg of the route through New Jersey and New York into Canada.

The plump bird that leaves winter homes as far south as Tierra del Fuego near the tip of Argentina arrives on the East Coast sparrow-thin — and needs the crab eggs to survive the rest of the trip.

But a decline in the population of horseshoe crabs, which are used mostly as commercial fishing bait, and the thousands of eggs each bird needs to replenish itself have pushed the tourist and bird-watcher favorite toward extinction.

One New Jersey study found the population of the salmon-breasted bird reaching a healthy weight dropped sevenfold from 1998 to 2002. Total population is estimated at 70,000, down from 150,000 in the 1980s, according to the Audubon Society. Wildlife groups predict extinction within a decade.

Audubon and other environmental and wildlife groups are working with officials from Maryland, Delaware, New Jersey and New York to help the bird by limiting the horseshoe crab harvest. In March, the Atlantic States Marine Fisheries Commission adopted limits on how many horseshoe crabs could be taken beginning this spring.

“This is unprecedented and may even be unprecedented nationally,” said Brad Spear of the federally funded consortium of states from Maine to Florida.

Robert Munson, 71, wishes as much concern was felt for his fellow commercial fishermen.

“I think they have gone far beyond what is necessary,” said Munson, now retired and living in Newport, N.J.

He thinks the harvest limit has less to do with the bird migration and more to do with the tourist migration from New York and Philadelphia to see it.

“If you want to bring in the tourists … and if the birds aren’t there, you’re in trouble,” he said Thursday.

The states in the commission followed the lead of New Jersey and Delaware, which in recent years enacted limits. New Jersey and Delaware supported a more than 50 percent cut in the harvest, to 150,000 crabs a year for each state.

Maryland, which several years ago voluntarily limited its harvest to 211,000, agreed to an annual cap of 170,000 crabs.