WASHINGTON (CN) – The U.S. Fish and Wildlife Service plans to list as threatened a sandpiper that flies 9,300 miles from the southern tip of Argentina to the Canadian arctic every spring and back again in fall. The FWS says climate change and the overharvest of horseshoe crabs threaten the birds.
The listing proposal for the rufa red knot was spurred by a 2011 settlement between the USFWS and the Center for Biological Diversity (CBD) that resulted in a five-year workplan to speed listing decisions under the Endangered Species Act for hundreds of species across the county.
The knot is a medium-sized bird with a 20-inch wing span. These intrepid birds travel up to 19,000 miles annually and fly thousands of miles without stopping. One banded bird has been nicknamed Moonbird “as researchers estimate his 20 or more years of migrations are the equivalent of a trip to the moon and at least halfway back,” the USFWS noted in its press release.
Delaware Bay provides an extremely important stop-over for the birds, where they nearly double their weight dining on horseshoe crab eggs before completing the final leg of their migration to their arctic nesting grounds, the action said.
“In some areas, knot populations have declined by about 75 percent since the 1980s, with the steepest declines happening after 2000,” the USFWS’ Director Dan Ashe was quoted as saying in the agency’s press release. A big factor in that decline was caused by commercial harvest of horseshoe crabs, the agency said.
A 2012 Atlantic States Marine Fisheries Commission management framework ties horseshoe crab harvest levels directly to knot recovery targets. The USFWS maintains that this framework “should ensure no further threat to the knot from the crab harvest,” the agency said, while also acknowledging that the crab population has not yet fully recovered.
“The scarcity of horseshoe crabs is being caused by major harvest increases, since the 1990s, for bait in the eel- and conch-fishing industries and for biomedical use,” the CBD noted in its statement. The crab blood is harvested for a clotting agent “that makes it possible to detect human pathogens in patients, drugs, and intravenous devices,” the action said. Since the mortality rate for crabs that are bled for the clotting agent is up to 30 percent, those crabs are increasingly being used for bait instead of being released in an effort to reduce total mortality rates, the action said.
Climate change affects the knots by disrupting the timing of departures and stopovers and by affecting the snow cover in the arctic tundra where the birds breed. Climate change also impacts food resources in coastal habitats affected by rising sea levels and storm and weather patterns, according to an agency fact sheet. The window of opportunity for arctic summer courtship and raising young is narrow, and if climate change has affected the seasonal supply of food sources on the migration path then the birds suffer from a timing mismatch.
“Northbound shorebirds migrate in a sequence of long-distance flights alternating with periods of intensive feeding to restore energy reserves. Most of the energy stores are depleted during the next flight; thus, a bird’s ability to accumulate a small additional energetic reserve may be crucial if its migration gets delayed by poor weather or if feeding conditions are poor upon arrival at the next destination,” the action said.
“Scientists have estimated that nearly 90 percent of the entire population can be present on the Delaware Bay in a single day. Moving in large flocks is probably an adaptation against predation, but also makes the red knot vulnerable to habitat change and loss of site-specific food sources, like the horseshoe crab,” the CBD said.
The USFWS plans to propose critical habitat for the birds before the end of the year.
Comments and information on the proposed listing rule are due by Nov. 29.
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