Volunteers from around the world converged on southern Delaware in May in the latest effort to save one of America’s most imperiled shorebirds, the red knot.
The annual drive to capture, count, measure, and tag the remarkable long-distance migrants this year drew workers from at least seven foreign countries including Pakistan, South Korea and Malaysia.
The team of up to 25, led by the Delaware Division of Fish & Wildlife, spends most of May monitoring the birds as they arrive on Delaware Bay beaches en route from wintering grounds as far away as southern tip of South America to their breeding territory in Arctic Canada.
It’s one of the longest migrations in the avian world, and is made possible only by the bay’s ubiquitous horseshoe crabs, whose eggs provide a critical source of food for the birds during their brief stopover, allowing them to complete the 9,000-mile annual journey.
They arrive at the Delaware beaches having lost about half of their body weight – normally less than five ounces – after flying up to 3,000 miles nonstop from Brazil. They have to regain that weight in only 10-14 days in order to resume their northward migration and have any hope of breeding successfully.
Efforts to conserve species previously in decline
In the early 2000s, numbers plunged to levels that raised fears that they were headed for extinction. Crab numbers had plummeted because of overharvesting by commercial fishermen in the 1990s, depriving the birds of the eggs, and decimating their population.
Since then, Atlantic states have limited the catch of horseshoe crabs in a bid to rebuild populations of both crabs and knots. Delaware allows the harvest of male crabs only, and that too only after June 7 each year, once the knots leave the Bayshore; New Jersey has banned the crab harvest altogether.
In the last few years, the bird’s numbers have shown the first signs of recovery but biologists say it’s still nowhere near the level where the species is large enough to survive natural calamities like Arctic storms that can wipe out breeding colonies.
This year, it’s too soon to say whether the red knot’s numbers are continuing to build. By May 26, Delaware’s workers had counted about 1,000 individual birds wearing leg tags that were attached in previous years. Since about 10 percent have been tagged, the latest count suggests about 10,000 birds had moved through the bay by that date
That’s a low number compared with recent years, but it might be a sign that the birds are dispersing over a wider area of the bay to feed on the tiny green crab eggs that are known to be plentiful this season. If so, that would make them more difficult to count than in previous years, and might explain this year’s apparent scarcity of birds, said Kevin Kalasz, a wildlife biologist with the Division of Fish and Wildlife, and the leader of the annual red knot count.
In 2011, an increase in the number of birds heading south in the fall migration indicated that it had been a successful breeding season. Since it takes two years for young birds to become full migrants, biologists are looking for evidence of a corresponding increase in this year’s northward migration. If so, 2013 could be an important year for the red knot, Kalasz said.
Delaware’s official count won’t be known until later this year, when it will be combined with the tally from the New Jersey side of the bay. Last year, the total population was estimated at 44,000, an improvement from the low of 15,000-20,000 that caused alarm a few years ago but still well short of the level that would represent a victory for the conservationists.
Even if the bird is on track for recovery, it could still be derailed by sea-level rise which is beginning to show itself along the Delaware coast, and is projected to inundate most of the state’s beaches by the end of the century. But the habitat could be preserved by beach replenishment or by the acquisition of land to allow beaches to retreat inland as rising tides encroach, Kalasz said.
He declined to say how many birds would represent a fully recovered population, but suggested that the red knot appears to have moved out of the danger zone for now.
“I don’t think we are out of the woods,” Kalasz said. “But there is no extinction risk in the next few years. We’ve at least stabilized the population.”
Volunteers monitor annual migration
During a recent visit to Mispillion Harbor, an estimated 230 red knot sat tightly packed on several islands along with numerous other shorebirds including semipalmated sandpipers and ruddy turnstones. Suddenly, thousands of birds rose off their roosts, wheeling and swooping in fear as a peregrine falcon flew over in search of the small shorebirds on which it preys.
Sights like those help explain why volunteers from around the world come to Delaware each year to monitor the red knot and other shorebirds. Their duties include using nets to capture roosting birds and then assessing their weight and health before releasing them with tiny green identification tags fixed to their legs; spotting individuals that are carrying tags affixed in previous years, and recording all the data.
Volunteers live and work in a rented shore house at Slaughter Beach where the lucky ones get beds while the rest sleep on the floor or outside in tents.
For the last 15 years, the team has included Nigel Clark, a senior official with the British Trust for Ornithology, who first participated as a paid consultant because of his extensive experience with shorebird conservation in other parts of the world, and is now a volunteer.
This year, Clark rediscovered the “Moonbird,” the oldest known individual red knot that was first tagged in 1995, and is so named because its migration, at some 20,000 miles a year, has totaled more than the distance between the earth and the moon. The bird, known also by its leg tag B95, was not seen in 2012, raising fears that it had finally died, but was spotted on May 16 in Mispillion Harbor.
Aside from the red knot, Clark said he’s drawn from his home in Britain each year by the magnitude of the Delaware Bay’s spring shorebird migration which he said is the biggest, and most accessible, on the planet.
At Mispillion Harbor, Clark and other volunteers stood a few yards from an estimated 40,000 feeding shorebirds early Sunday morning, a spectacle that he said only happens on the Delaware Bay.
“There’s nothing like that anywhere else in the world,” he said.
Photo courtesy: Kevin S. Kalasz, Delaware Div. of Fish and Wildlife .
