Horseshoe crabs are
an important part of the Delaware Bay's Food Web.
Free Buffet for the Birds
Once a year,
in the spring, over a million shorebirds fly more than 2,000 miles to the
Delaware Bay arriving just in time for a “Free Buffet”!
phot permission: Nancy Carol Willis
The Delaware Bay plays host to the second
largest population of migrating shorebirds in North America. Up to 80 per
cent of the entire populations of some shorebirds pass through this area
every spring. The buffet that I’m talking about is the one that includes
only horseshoe crab eggs. You see, many birds from Central America, Peru,
Surinam, and Argentina’s Terria del Fuego in South America, including red
knots, sanderlings, ruddy turnstones, and sandpipers stop in the Delaware
Bay area, on their way to Northern Canada, to feast on these eggs. These
famished shorebirds have been migrating for quite some time, and they need
some kind of food for energy to continue their journey north where they
will mate, make their nests, and lay their eggs before it starts getting
cold in the middle of August. Well, horseshoe crab eggs are just the kind
of boost that these shorebirds need. The birds arrive exhausted and suffering
from weight loss. They eat many times their weight in horseshoe crab eggs,
quickly recover, and continue their journey. While the birds feed on the
eggs, they may gain double or even triple their weight before they start
migrating again. A typical bird will eat one egg every five seconds, 14
hours a day. It is estimated that the birds eat over 8,000 eggs per day
during their three week visit. That’s about 300 tons of eggs a season.
The birds do not eat the eggs that are buried deeper in the sand, but the
eggs that are exposed by repeated nest digging and wave action. In the
last 2 weeks of May, the Delaware Bay beaches sometimes have between 500,000
and 1,500,000 shorebirds alone!
photo permission: David Carter
Other birds also
dine on the horseshoe eggs. In addition to eleven types of shorebirds,
three kinds of gulls, cowbirds, grackles, mourning doves, house finches,
starlings, house sparrows, and even pigeons feed upon these eggs.
More information
and pictures of shorebirds
Monitoring
shorebirds
Places to
see shorebirds in the spring when they stop in the Delaware Bay area
Other Animals Like Horseshoe Crabs, Too
Birds aren't the only animals that like to eat the eggs. People have seen
eels work their way under spawning females and gulp down all the eggs as
they are laid. Minnows, juveniles of larger fish including striped
bass, raccoons, foxes, and turtles also eat the eggs. Also, the threatened
Atlantic loggerhead sea turtles and sharks eat the adult horseshoe crabs.
Horseshoe crabs make up the main diet of juvenile loggerhead turtles, particularly
in the Chesapeake Bay, and the adult turtles flip large crabs over and
chomp off the legs and then eat most of the muscles inside the shell. Sharks
swallow horseshoe crabs whole.
Back to uses of
horseshoe crabs
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