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Written by Bryan Watts
March 13, 2010
A red knot, just before its release. Photo by Bryan Watts.
The mid-Atlantic Coast is a terminal staging area where the rufa population of red knots stops in spring to prepare for the last leg of its migration to breeding grounds in the high Arctic. Numbers stopping over in Delaware Bay, the most significant mid-Atlantic staging area, have declined by nearly 90% over the last 30 years. These precipitous declines have been consistent with numbers estimated within Tierra del Fuego, the largest wintering site leading to its listing as endangered in Canada and a petition for listing in the United States. In Delaware Bay, red knots depend on horseshoe crab eggs to rapidly restore fat reserves before departing. Overharvest of horseshoe crabs in Delaware Bay and the related degradation of foraging conditions has been one of the leading factors proposed to explain knot declines.
The Virginia Barrier Islands represent a second, spring staging area for red knots within the mid-Atlantic. The island chain includes more than 100 kilometers of open beach and represents one of the most pristine set of coastal barriers remaining in North America. Unlike Delaware Bay, the islands support no significant spawns of horseshoe crabs. Red knots that stage along the islands feed on clams within the surf zone and mussels on intertidal peat deposits. A band resight program conducted by CCB since 2006 is only beginning to reveal the relationship between the barrier islands and the Delaware Bay staging areas (see the recent article: Red knot resight data indicates flux between two migration staging areas).
The same flight crew has conducted aerial surveys along the Virginia Barrier Islands since 1994. Pictured are surveyor Bryan Watts (left), recorder Barry Truitt (middle), and pilot Carter Crabbe (right). Photo by Libby Mojica.
The Center for Conservation Biology (CCB), in partnership with The Nature Conservancy, initiated weekly aerial surveys for shorebirds along the Virginia Barrier Islands in the spring of 1994. Unlike in Delaware Bay, peak numbers of red knots in Virginia have not shown dramatic declines over the past 15 years. This seems to suggest that prey resources may have been more stable within the Virginia Barrier Islands site compared to Delaware Bay. The nature of the prey base is quite different between the two staging areas. CCB is continuing work that focuses on stopover ecology along the barrier islands and the broader interaction between mid-Atlantic staging areas.
Project sponsored by the Center for Conservation Biology (CCB), The Nature Conservancy (TNC), Virginia Department of Game & Inland Fisheries (VDGIF), and Virginia Department of Conservation & Recreation Natural Heritage Program (VDCR NHP).