The red knot, a robin-sized shorebird, makes one of the longest annual migrations of any bird — an 18,000-mile round trip between the southern tip of South America and the Canada Arctic. To complete this journey, red knots refuel along the mid-Atlantic coast for a few weeks each May.
Coastal development, climatic changes, and an altered food supply make this an increasingly risky expedition for the little bird. Red knot populations are now less than half that of 30 years ago, and the bird is a candidate for Endangered Species Act protection. Researchers in the College of Natural Resources and Environment's Department of Fish and Wildlife Conservation have spent the past seven years studying the red knot’s diet and habits for clues to its decline.
“The red knots probably declined in part because of the decrease in the horseshoe crab populations in the Delaware Bay, but other factors may play an important role,” said Professor Jim Fraser, a nationally known wildlife researcher.
Although previous research suggests links between the red knot’s decline and waning horseshoe crab egg availability in the Delaware Bay, Virginia Tech’s researchers are investigating whether this is the whole story. Their studies show one-third of the migrating red knots stop to refuel along Virginia’s Eastern Shore, where they don’t rely on horseshoe crab eggs.
“Red knots love coquina clams, an eighth-inch hardshell clam abundant on the barrier islands on Virginia’s Eastern Shore,” said Assistant Professor Sarah Karpanty, Fraser’s co-investigator. “This is one of the wildest sections of the Atlantic Coast left in the U.S. and a special place for birds.”
This is the first systematic study of red knots in Virginia. The research team uses methods such as flyovers, cannon-propelled net capture, and tagging to sample and evaluate the birds’ numbers and relative health and track their movements using radio receivers.
Racing against hard biological deadlines to reach its destination, breed, and raise its young within the short Arctic summer, the bird relies on an abundant food supply and a healthy coast. If these natural systems are out of balance, it puts the bird in serious trouble, a signal that much more is imperiled.
The red knots arrive on Virginia’s barrier islands in mid-May, emaciated and voracious, and have been observed foraging through the night. “Many must at least double their body weight before they take off, in order to successfully reach their nesting areas and have their young,” Karpanty said.
In addition to Fraser and Karpanty, the team includes Research Assistant Professor Dan Catlin, project manager Shannon Ritter, and Jonathan Cohen, a former Virginia Tech research scientist who is now an assistant professor at the State University of New York College of Environmental Sciences and Forestry, as well as collaborator Barry Truitt of The Nature Conservancy. Volunteer and paid technicians, including Erin Heller, a 2011 wildlife science graduate, are an important part of the team.
While studies concentrate on the birds’ migration feeding habits, less is known about their breeding ecology. One clue to the bigger puzzle might be the lemming. The decline of this small rodent, famous for its three- to four-year boom-and-bust population cycles in the Arctic tundra, may affect red knot numbers.
“When lemming populations are down, their predators, owls and foxes, may start eating red knots,” Fraser hypothesizes. “In part of Northern Europe, though, the cycle stopped for five to 10 years. No one knows what lemming populations were doing in the Canadian Arctic during the period of red knot decline, but if the cycling stopped there, red knot reproduction may have declined in response.”
Fraser, Karpanty, and Cohen are applying for grants to study the birds’ Arctic behavior and have a paper in review documenting that red knot populations cycled with lemming populations before the red knot decline. Meanwhile, Fraser’s team was back down on the Eastern Shore in May 2012 to continue the research.
“From the Arctic to the coast of Virginia, we must work to understand the effects of human activities on shorebird population dynamics if we are to sustain our shorebird populations” Fraser said, “but beyond that, we must develop the collective will to conserve and restore remaining fragments of wild, undeveloped coastline. Only by combining science with the will to conserve can we ensure that our grandchildren will witness the incredible spectacle of shorebird migration.”
Wildlife Professor Jim Fraser and research scientist Jonathan Cohen attach a satellite transmitter to a red knot using an elastic harness that eventually degrades and allows the transmitter to fall off of the bird.
Lynn Davis, the communicator for the College of Natural Resources and Envirnoment, spent a week with the research team on Virginia’s Eastern Shore and barrier islands and documented the researcher’s day-to-day field work.
A PBS documentary examines the connection between red knots and horseshoe crabs.
The remote barrier islands off Accomac and Northampton counties on Virginia’s Eastern Shore create a buffer between the Eastern Shore and the Atlantic Ocean. They provide a critical stopover and feeding site for many species of migratory shorebirds, including the imperiled red knot.
The 60-mile-long chain of islands, most of which are protected by Virginia’s Nature Conservancy and other partners, serves as one of the most important migratory bird habitats on Earth and makes up the longest expanse of undeveloped shoreline and coastal wilderness on the East Coast.
The barrier islands are shifting strands of sand and marsh. The sand is driven along the Atlantic coast by wind, waves, and currents. What is lost from the end of one island may be gained by the tip of another. The shifting sands, combined with annual rises in the sea level, may cause the islands to completely disappear someday.
“One of the greatest emerging challenges to red knot conservation in particular, and shorebirds in general, is how sea level rise will impact these barrier islands used for their stopovers,” said Assistant Professor Sarah Karpanty of the Department of Fish and Wildlife Conservation.
Red knots gather in large numbers on Virginia’s barrier islands during their 9,000-mile migration from South America to the Canada Arctic. Photo courtesy of Barry Truitt.
Take a look back at previous Spotlight features in our archive.