VCU news

By Sathya Achia Abraham

Each year, the red knot sets out on one of the longest migrations of any animal known in the Western Hemisphere. Traveling from the southern tip of South America to its breeding grounds in the high Arctic, it earns frequent flyer points for a flight totaling more than 9,000 miles. Not bad for a medium-sized shorebird.

As a long-distance migrant, red knots remain almost completely coastal during migration, feeding mostly on mussels and clams. An exception is those that stop in the Delaware Bay and feed on horseshoe crabs.

Others in the group make their mid-Atlantic pit-stop here, in Virginia, on their way from Tierra del Fuego in South America. The condition in which they leave Virginia and head northward is critical to their ecology.

“Red knots are sensitive indicators of coastal health. And this particular species staging in Virginia may also be an indicator of climate change because they breed so far to the north and they migrate over such a long distance,” said Bryan Watts, Ph.D., director of the Center for Conservation Biology, a unit within the Virginia Commonwealth University Rice Center through a partnership between researchers at VCU and The College of William & Mary.

Through a conservation initiative, researchers at the Center for Conservation Biology and The Nature Conservancy are learning more about these shorebirds’ migratory pathways and habits and the importance of Virginia to their journey.

“Virginia is a staging ground for the species,” Watts said. “It’s the last stop where they refuel before flying up to the breeding grounds in the Arctic. So it matters what stage they leave in because the conditions when they arrive on the breeding grounds aren’t that great. The females need to have enough energy to produce a clutch.”

Red knots threatened
Each spring since 1994, Watts, together with research partner Barry Truitt of The Nature Conservancy, have flown weekly aerial surveys for migratory shorebirds along the Virginia Barrier Islands. And, since 2006, the pair has participated in a coordinated survey with other states along the Atlantic Coast during the peak week for red knots.

As part of this effort, Watts also has flown the coasts of New Jersey, Delaware, Maryland, Virginia and North Carolina.  He said that combined estimates for the entire coast have remained relatively stable for the past four years, amounting to between 24,000 to 28,000 birds.

But, overall, there has been a population decline of approximately 90 percent since the late 1970s, making the red knot a candidate species for federal listing under the Endangered Species Act.

According to Watts, Virginia is second only to New Jersey in the number of red knots supported and typically accounts for 25 to 35 percent of the coast-wide total. The number of birds staging in Virginia has remained more stable than Delaware Bay, where there have been sharp declines due to dwindling availability of the horseshoe crab.  

“Most of the decline that has been seen occurs in the Delaware Bay,” Watts said. “If you look at Virginia’s numbers from the mid-1990s, they’ve held up well. Virginia has been a stronghold for the species.”

He said the Virginia population numbers have fallen slightly in the last 15 years, but only by about 15 percent – not nearly the 80 or 90 percent that has been observed in Delaware Bay.

Watts said that it is important to note that unlike the linkages between red knot declines and horseshoe crab harvests in Delaware Bay, red knots staging in Virginia do not depend on horseshoe crab eggs. Staging birds in Virginia feed on clams and mussels within the surf zone as they do in coastal staging areas elsewhere throughout their range.

Layover in Virginia
Red knots typically begin to arrive in Virginia in the first weeks of May, but the numbers grow most during the third week, which many experts consider to be the peak period. They begin to move out in large numbers, Arctic-bound, in early June.

Watts and his team began weekly surveys starting the last week of April and will continue through early June.

Through a large multi-year study, Watts and his team have been examining stop-over duration of the shorebird. By reading the bands of tagged birds, they get an idea of how long the birds are staging in Virginia.

The team has discovered a number of things that have impacted its perspective of what is taking place with the species. Team members have learned there is a lot of movement back and forth between Virginia and Delaware Bay. They have seen birds in the Virginia Barrier Islands and Delaware Bay, after examining their bands. Approximately 30 percent of the birds located in Virginia also are being detected in the Delaware Bay. Further, they have detected the birds not only moving from Virginia to Delaware Bay but also moving from Delaware Bay to Virginia.

“There is this back and forth between these two staging areas and that really changed the scientific view of the species, since it was initially thought that Delaware Bay was a closed system where they were coming specifically to Delaware Bay, fattening up and then leaving,” Watts said. “But it’s not really that way – it’s open – it’s really a mid-Atlantic complex of staging areas … and this points to the real importance of Virginia to the species.”

Making room
For the past two years, Watts has conducted aerials in the Outer Banks of North Carolina and noted upwards of 10,000 to 15,000 people and approximately 1,000 red knots on the beach.

Watts said that those numbers point to the issue that the Atlantic coast may not be providing enough beachfront habitats for some of these shorebird species. In the Outer Banks, for example, red knots have access to perhaps 5 percent of the beach that they once could access.

“We are drowning out a lot of these species,” Watts said. “This goes to the broader question: What can we offer these species and how do they fit into society?”