CLIPBOARD : FORSTER’S TERN (Sterna forsteri)

Description: This slender water bird has pointed wings and a deeply forked tail. It’s white from neck to rump with light gray above; tail has white outer edges. Summer markings include a black-capped head and black-tipped beak; legs and feet are orange. Plumage changes in fall as cap molts and is replaced with a black mask across eyes; beak and legs become dark. White frosted wing primaries distinguish forster’s tern from common and elegant terns. Immature has cinnamon-colored cap with a dark patch over eye. Length: 14 1/2 inches.

Habitat: Bolsa Chica wetlands, beaches and rivers; fresh or saltwater.

Diet: Insects, fish and frogs.

Displays: Unknown.

Nest: Elaborate, woven platform of reeds scraped onto mud flat; occasionally uses nest of western grebe.

Eggs: Light brown marked with dark brown. Length: 1.7 inches.

Call: Nasal za-a-ap or a short, harsh kyarr .

Notes: Hollow bones and numerous air sacs enable the forster’s tern to dive for fish from a great height, the momentum propelling its body beneath the surface. This tern seldom swims.

Map indicates 5-kilometer-square areas where breeding activity has been confirmed.

Note: Map is divided into 5-kilometer squares so that Audubon Society volunteers can more easily survey areas on a regular basis. Sources: Sea and Sage Audubon Society; “The Birder’s Handbook,” Ehrlich, Dobkin and Wheye, Fireside Books (1988); “Field Guide to the Birds of North America,” National Geographic Society (1987); “Birds of Southern California: Status and Distribution,” Garrett and Dunn, Los Angeles Audubon Society (1981).