As
a group, shorebirds undertake some of the most spectacular
of long-distance migrations of any North American birds.
Nearly two-thirds of the species that breed in North America
journey from their arctic nesting grounds to winter in
Central and South America, and then return to the Arctic the
following spring. Many species traverse more than 15,000
miles in this annual circuit. Some fly at altitudes
exceeding 10,000 feet and achieve cruising speeds
approaching 50 mph. From sightings of marked individuals, we
know that at least some birds on nonstop flights cover
nearly 2,000 miles in less than two days. Hudsonian Godwits
may fly 8,000 miles nonstop between breeding and wintering
areas, unless brief stopovers are made at
as-yet-undiscovered spots somewhere in South America. The
surprising migration feats of Sanderlings were discovered
only recently by ornithologist Pete Myers. Their hitherto
unsuspected circumnavigation of the Americas each year
follows a route east across the top of North America and
down the Atlantic coast in the autumn to their wintering
grounds in Chile and Peru, and back north in the spring
through the western United States to their arctic breeding
grounds. Although
more than 20 million shorebirds migrate through the United
States to the Arctic each year, Myers and his colleagues
have captured the attention of the ornithological and
conservation communities with their recent discovery that
the long-term survival of even abundant species may be in
jeopardy. Their studies show that Sanderlings, Ruddy
Turnstones, Red Knots, Dunlins, and White-rumped, Baird's,
Stilt, Western, and Semipalmated Sandpipers form enormous
concentrations at several key staging areas along their
migration route. Each of these spots is critical for
successful migration of these species, providing
superabundant food resources that enable the birds to
quickly replenish their energy reserves and continue on. In
North America, five such sites support more than a million
shorebirds annually: Alaska's Copper River Delta,
Washington's Gray's Harbor, eastern Canada's Bay of Fundy,
Kansas' Cheyenne Bottoms, and the beaches of Delaware Bay in
New Jersey and Delaware. More than 80 percent of the entire
North American population of some species may join ranks at
any of these key locations; virtually all Western Sandpipers
and Dunlins use the Copper River site. Other similarly vital
locations have been identified throughout the Americas.
These few critical staging areas underpin the entire
migration system of New World shorebirds. As Myers points
out, such enormous concentrations dependent upon so few
widely spaced locales breaks the usual link between a
species' abundance and its immunity to
extinction. The series
of critical stopover sites is typified by Delaware Bay. The
arrival and departure of 500,000 to 1,500,000 shorebirds
within a span of three to four weeks is synchronized with
the annual breeding cycle of the bay's enormous population
of horseshoe crabs, for it is the eggs of the crabs that
supply the energy required by the birds to complete their
spring journey to the Arctic. Each evening, after day-long
feasting on crab eggs, the birds move east to roost in tidal
marshes and on the outer beaches of the Atlantic coast.
Coastal and wetland development have forced the birds into
ever smaller foraging and roosting sites as the number of
suitable areas has dwindled. On high-tide nights, more than
100,000 shorebirds may be packed into a few hundred yards of
beach. Fortunately,
efforts are now under way to link the staging sites
connecting wintering and breeding areas into a system of
sister reserves. Shorebird biologists, backed by the World
Wildlife Fund - U.S., the International Association of Fish
and Wildlife Agencies, and the National Audubon Society are
working toward establishment of these critical reserves
throughout the Americas. Success hinges on persuading local,
regional, and national governments that such a system is not
only desirable but absolutely necessary to ensure the
survival of migratory shorebirds. As a first step, in May of
1986 the governors of New Jersey and Delaware mandated the
lower estuary of Delaware Bay as a reserve for shorebird
conservation. SEE:
Spacing
of Wintering Shorebirds;
Shorebird
Feeding;
Sandpipers,
Social Systems, and
Territoriality;
Birds
and the Law;
Migration. Copyright
® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl
Wheye.