Parasitic JaegerStercorarius parasiticus

adult, light morph, breeding
Arthur Morris/VIREO
juvenile, light morph
Herbert Clarke/VIREO
adult, light morph, breeding
Bill Schmoker/VIREO
adult, dark morph
Arthur Morris/VIREO
adult, intermediate morph
Glenn Bartley/VIREO
adult, light morph, breeding
Arthur Morris/VIREO

Description

This is the mid-sized member of the jaeger trio, and the most familiar, as it is the one most likely to be seen from shore. Variable in plumage, it occurs in dark, light, and intermediate morphs.

Habitat

Ocean, coastal bays, lakes (rarely); tundra (summer). Spends most of year at sea, concentrating over continental shelf within a few miles of land, rarely far out in mid-ocean. Breeds in open country of far north, mostly tundra, also rocky barrens and coastal marshes. Immatures and non-breeders may remain at sea all year.

Feeding Diet

Includes fish, birds, rodents. Diet at sea and at coastal nesting areas is mostly fish stolen from other birds. On land, also eats many birds and their eggs, rodents, insects, berries. Less dependent on lemmings and other rodents than the other jaegers.

Feeding Behavior

At sea, does much of foraging by chasing other birds and forcing them to drop their catch; also dips down in flight to catch fish at surface. On breeding grounds, also hovers and swoops down to catch prey, and feeds while walking.

Nesting

Usually first breeds at age of 4-5 years; in one study in Europe, birds of pale morph tended to start nesting younger than dark birds. May nest in colonies or in isolated pairs. Early in breeding season, pairs or groups perform acrobatic display flights. Courtship involves upright posturing, calling; male feeds female. Nest site (selected by male) is on the ground in the open, sometimes on a slight rise. Nest (built mostly by female) is a shallow depression, usually with a sparse lining of plant material. Eggs: 2, sometimes 1-3. Olive to brown, rarely blue, spotted with brown. Incubation is by both sexes, 25-28 days. Young: Downy young may leave nest a few days after hatching, but remain in vicinity. Both parents feed young, by regurgitation. Young can fly at 25-30 days, but remain with parents for a few more weeks.

Eggs

2, sometimes 1-3. Olive to brown, rarely blue, spotted with brown. Incubation is by both sexes, 25-28 days. Young: Downy young may leave nest a few days after hatching, but remain in vicinity. Both parents feed young, by regurgitation. Young can fly at 25-30 days, but remain with parents for a few more weeks.

Young

Downy young may leave nest a few days after hatching, but remain in vicinity. Both parents feed young, by regurgitation. Young can fly at 25-30 days, but remain with parents for a few more weeks.

Conservation

Most of breeding range is remote from human impacts. No evidence of major changes in population.

Range

Often seems to follow general trend of coastline, a few miles offshore; some may regularly migrate over land. A few remain in winter as far north as North American waters but most go farther south, some reaching southern Australia, Africa, South America.

Listen

various calls

Similar Species

adult, breeding

Heermann's Gull

Every summer, flocks of these distinctive gulls move north along the Pacific Coast from their nesting grounds in western Mexico. This movement is timed with the northward flight of Brown Pelicans; when a pelican comes to the surface after plunging into the water for fish, a Heermann's Gull is often waiting to try to snatch the fish from the pelican's pouch. Although this gull is not large, it is aggressive, harrying other birds to make them drop their catch.

adult

Long-tailed Jaeger

A swift-flying seabird, extremely graceful and agile in flight. When swimming, it floats buoyantly, and it takes flight from the water easily. Of the three jaeger species, the Long-tail is the smallest and the one that migrates farthest offshore; south of the Arctic, it seldom comes within sight of land.

adult, breeding, light morph

Pomarine Jaeger

Powerful and fast-flying, a predator and pirate of the ocean and the far north. The largest of the three jaeger species. Not seen from shore as often as Parasitic Jaeger, but usually the one seen in greatest numbers on boat trips offshore. In northern Alaska, this is a major predator on the brown lemming: During summers when these rodents are in low numbers, many Pomarine Jaegers do not attempt to nest.

Vireo

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