In size and habits, the mighty Caspian Tern bridges the gulf between smaller terns and raucous gulls. It is the largest tern in North America, and its wing beats are slower and more purposeful than those of small terns; in flight, the Caspian Tern can be confused with gulls. These blood red-billed terns are often seen in association with gulls on exposed sandbars or mudflats. As Ring-billed Gulls expand their range to the north and west in North America, the Caspian Tern follows these pioneers to establish breeding colonies. There is perhaps no other bird that possesses such an odd North American breeding distribution as the Caspian Tern. Isolated pockets of these terns breed sparsely in Utah and Wyoming, along the Pacific Coast, in the Mackenzie district in the Northwest Territories, around the Great Lakes and in Newfoundland. This species was first collected on the Caspian Sea in Asia, hence its name.
I.D.: Sexes similar: black cap; heavy, blood red bill; light gray wing covers; black legs; shallowly forked tail; white underparts; long, frosty, pointed wings.
Size: L 19-23 in. (48-58 cm);
W 50-55 in. (127-140 cm).
Range: rare migrant in the U.S. Rockies; local breeder in the central and northern U.S. Rockies.
Habitat: In migration: shorelines and over large lakes, wetlands and rivers up to the montane.
Nesting: in the Rockies, only on Molly Island on Yellowstone Lake; in a shallow scrape on bare sand, dirt or rocks; nest is sparsely lined with vegetation, rocks or twigs; pair incubates 1-3 eggs for 20-22 days.
Feeding: hovers over water and plunges headfirst after small fish, tadpoles and aquatic invertebrates; also feeds by swimming and gleaning at the water's surface.
Voice: low, harsh ca-arr; also a loud kraa-uh.
Similar Species: Common Tern and Forster's Tern: much smaller; lack the heavy, red bill.