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Bryan Brillhart Photography Presents Dig Imperial Beach "Bird of the Week", the "Caspian Tern"

May 12, 2016 10:50PM ● By Paul Spear

Bryan Brillhart of Bryan Brillhart Photography presents us with the Dig Imperial Beach “Bird of the Week”. This week’s bird is the "Caspian Tern (Hydroprogne caspia, formerly Sterna caspia)"

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Bryan Brillhart Photography

Caspian tern (Hydroprogne caspia, formerly Sterna caspia)

This week’s “Bird of the Week” is the Caspian tern (Hydroprogne caspia, formerly Sterna caspia), the largest of the terns with a length of 48–60 cm (19–24 in), a wingspan of 127–145 cm (50–57 in) and a weight of 530–782 g (18.7–27.6 oz), It is larger than many gulls. Adult birds have black legs, and a long thick red-orange bill with a small black tip. They have a white head with a black cap and white neck, belly and tail. The upper wings and back are pale grey; the underwings are pale with dark primary feathers.

The Caspian gull is cosmopolitan, nesting on five continents. In North America, it is common Habitat is in large lakes, coastal waters, beaches, and bays. They can be found on both fresh and salt water, favoring protected waters such as bays, lagoons, rivers, and lakes, not usually foraging over open sea. Inland, they are more likely on large lakes than on small ponds. Nests are on open ground on islands, and on the coast. along both coasts and locally inland, mainly around large bodies of water. Noted for its long adolescence, with the young dependent on their parents for many months; even in late winter, many an adult Caspian is trailed by a begging youngster from the previous nesting season. Overall, populations are probably stable, perhaps increasing slightly; range has expanded recently to include southern Alaska.

When foraging, they fly high over water, hovering, then plunging to catch fish below the surface of the water. Less often, they fly low, dipping down to catch prey at the water's surface. They may steal food from other birds. Their diet is mostly fish, and they often concentrate on a few abundant fish species in a given locale (for example, shiner perch on California coast, alewife on Great Lakes). They also eat insects, and  sometimes eggs or the young of other birds.

Breeding is in spring and summer. After mating, females lay 1-3, rarely 4 or 5, pale buff, spotted with brown or black eggs. Incubation is by both parents (female may do more), in 20-22 days. Young may leave the nest a few days after hatching, moving to a nearby shore. If the colony is undisturbed, young may remain at the nest until ready to fly. Both parents bring food for young. Age at first flight about 30-35 days; young may remain with parents as long as 8 months.

Caspian terns first breed at the age of 3 years. They nest in colonies, but sometimes in isolated pairs. Males may fly low over the colony carrying fish; females follow. On ground, they display courtship feeding (male feeds female). Nest site is on bare ground, among driftwood or debris, perhaps sometimes on floating mats of dead vegetation. Nest (built by both sexes) is a shallow depression, sometimes with a rim or lining of debris.

The Caspian tern can be easily spotted flying along the Tijuana River in the Estuary. Look for this bird and the many other species that call Imperial Beach home. Until next week, good birding!


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