Tue June 18, 2013
Red Knots: A Bird Species on the Decline
Millions of birds passed through Virginia this spring, and the National Wildlife Federation says many are in trouble, in part because of climate change. A warming planet is drying up wetlands, causing more storms and producing less food. Sandy Hausman traveled to the Eastern Shore to report on one species -- the rust- colored sandpipers known as red knots. Each year, they fly about 10,000 miles – from the tip of South America to their nesting grounds in the Arctic – stopping in Virginia to refuel.
Bird watchers in North America used to see red knots as far north as Cape Cod, but today they’re most often seen in Virginia and in states around Delaware Bay. In the 80’s, experts counted more than 100,000, but over the last 20 years their numbers have fallen to an estimated 25,000.
There is some mystery surrounding the disappearing red knots. Virginia Tech Professor Jim Fraser says they might be having trouble finding food.
“Red knots eat horse shoe crab eggs, and with the over-harvest of horse shoe crabs, there may not be enough eggs.”
Here in Virginia, they also eat tiny surf clams called donax.
“You can see when the waves come in you can see donax riding in with the wave, and then as the wave recedes they’ll bury down in the sand, and in some cases we’d find maybe 300 clams in that little sampling.”
But when research specialist Shannon Ritter sifts the sand, she’s surprised by what she finds.
“I see one. Just one – pretty disappointing catch. That’s maybe two per cent of what we might expect to see at this time of year in a sample like this.”
Fraser says the surf clams might still be out to sea – waiting for waters off shore to warm, or populations might have been wiped out during their own breeding season when Hurricane Sandy played havoc with the marine environment.
Whatever the reason, when the red knots arrive here on Hog Island, just off the Eastern Shore, they’re little more than feathers and bones. They must eat, and student Meryl Friederich reports some knots did find food on the island’s peat banks – baby mussels.
“There was just an explosion of blue mussels and thousands of birds out there at a time, and it was really exciting to see.”
Last month official spotters from the Nature Conservancy and the Center for Conservation Biology boarded a Cesna and flew just above the beaches – searching for red knots and other shore birds. They reported far fewer knots on the Eastern Shore than last year. Professor Fraser thinks the birds could have gone elsewhere.
“It may be that they came, they looked around, and they said, ‘No food here. We’re going somewhere else.’ Preliminary results, and this is just chatter up and down the coast, is that there’s not a big treasure trove of knots somewhere that we don’t know about.”
It could also be that climate change prompted the birds to fly earlier than usual, but again, Fraser is doubtful.
“Species like the red knots that come from a very long distance are predicted to have a fairly rigid migration schedule, because they’re dependent upon food resources all the way. They’ve got to find food in Brazil. They’ve got to find food here on the east coast, and then they have to get to the Arctic.”
He offers one other intriguing theory. In the Arctic, where lemmings breed in a space between the snow and the ground, warming temperatures and melting snow have taken a toll. Lemming populations have not reached their usual peaks – which means arctic foxes, owls, hawks and weasels can’t feast on baby lemmings. Instead, they might be eating red knot eggs and babies.
“A number of years ago people realized that certain bird species only seem to breed well when the lemming populations were high, and the idea was that then the predators were going after the lemmings and leave the birds alone, so they get a chance to reproduce.”
Fraser and Ritter will return this summer to see if more donex clams have made a belated appearance on the shore, and they hope to find funding for more studies.
And until that mystery is solved, she, Fraser and other conservationists think the U.S. should declare red knots an endangered species. That would prompt more research and creation of a plan to help the birds recover.