Forster's Tern is similar to the
Common Tern, but its darker tail (inner web) distinguishes it. It
has the typical black cap on its head with slate grey back and wings,
with white breast and belly. Bill is yellow-orange with black tip.
Total length 35 - 38 cm (Godfrey, 1986).
Distribution
Columbia Basin: Within the province,
breeds only in the Columbia Basin at Duck Lake near Creston (Creston
Valley Wildlife Management Area).
Global: Breeds from se. British
Columbia, c. Alberta, c. Manitoba and s. Ontario south to California,
Nevada, Utah, Colorado, Kansas, Nebraska, Iowa, Indiana and Michigan;
along the Atlantic coast from s. New York locally to North Carolina;
and on the Gulf coast from Tamaulipas east to Louisiana. Winters
from c. California south to Guatemala and from Virginia south to
Florida and s. Mexico (Cannings, 1998).
Habitat
Forster's Terns nests singly or
in loose colonies on inland lakes and marshes, or on saltwater marshes
along the coast. Nest on floating mats of aquatic vegetation, Muskrat
houses, old grebe's nest, or in a depression lined with grasses
and pieces of shells (Cannings et al. In prep.).
Threats
The breeding population is estimated
at 12 pairs and is considered to be stable.
The breeding colony is protected
within the Creston Valley Wildlife Management Area, however, it
is moderately threatened by fluctuating water levels that can discourage
breeding. Although habitat is secure, there is potential disturbance
by fishers at Duck Lake, even though powerboats are not allowed.
Destruction of nests by waves during windstorms can be a problem.
Biology
Forster's Terns are capable of capturing
insects (e.g., dragonflies, caddisflies, and beetles) from the air
or off the surface of the water while in flight; they also dive
beneath the surface for fish. Birds probably arrive in British Columbia
during the second or third week of May, and dates for clutches range
from May 29 to July 10. Clutch size is 2 - 4 (usually 3) and the
incubation period lasts 23 - 25 days. Nestlings develop quickly
and both adults tend young until capable of flight, fledging at
3 - 4 weeks. Autumn migration may begin in late July but mostly
occurs in August (Godfrey, 1986.,Campbell et al. 1990., Cannings
et al. In prep.).
