http://www.eurekalert.org/pub_releases/2006-02/vt-hcd022106.php
Horseshoe crab decline threatens shorebird species
Public release date: 21-Feb-2006
Each year, the red knot, a medium-sized shorebird, makes a 20,000-mile
round-trip from the southern tip of Argentina to the Artic Circle – one
of the longest migrations of any bird. And each year from April to
June, the red knot stops over in the Delaware Bay to feed on horseshoe
crab eggs resulting from the largest spawning of horseshoe crabs found
on the East Coast of the United States.
Researchers from Virginia Tech and the New Jersey Division of Fish and
Wildlife have documented a reduction in the number of red knot birds
throughout the Delaware Bay tied to a decline in horseshoe crabs.
The research will be reported in The Journal of Wildlife Management, in
the article, "Horseshoe Crab Eggs Determine Red Knot Distribution in
Delaware Bay Habitats," by Virginia Tech fisheries and wildlife
research scientist Sarah Karpanty, professor Jim Fraser, and associate
professor Jim Berkson, New Jersey Division of Fish and Wildlife
biologists Lawrence Niles and Amanda Dey, and Virginia Tech statistics
professor Eric Smith. The article provides scientifically defensible
information for wildlife management officials as well as for other
members of the scientific community.
During their Delaware Bay stopover, the red knot nearly doubles its
body mass as it gorges itself almost exclusively on horseshoe crab
eggs. The purpose of this feeding frenzy is to ensure that the
shorebirds have enough energy to complete the trip north to their
breeding ground in the Artic.
However, due to horseshoe crab's popularity as bait used by fishermen,
the crabs appear to be in serious decline. At the same time, there has
been a great reduction in the total population of red knots, the report
notes. "The number of horseshoe crab eggs was the most important factor
determining the use of the beaches by red knots. The availability of
horseshoe crab eggs was even more influential than the presence of
human disturbance, predator occupation, and availability of other types
of food," says Karpanty, a post-doc in the College of Natural Resources.
The red knot's dependence on the horseshoe crab for survival has
attracted the interest of local, state, and international wildlife
management officials and researchers. Due to the red knot's unusual
migratory and eating behaviors, scientists from as far away as
Australia frequently travel to the Delaware Bay to study this rare
species.
"Biologists with the Delaware and New Jersey divisions of fish and
wildlife have been very helpful during this project, and they welcome
researchers from all over the world," says Fraser. "We hope to see
collaborative efforts like this continue so that we can learn how to
better manage wildlife resources like the red knot and horseshoe crab."
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