|Conservation status||Population has had ups and downs. Probably long-term decline (because of persecution at nesting colonies) until about 1920s, then gradual increase until 1950s. Numbers dropped again through 1960s, probably owing to effects of persistent pesticides. After DDT was banned in 1972, populations began increasing again, still increasing and expanding range through the present day. In some regions, wildlife management agencies have culled some nesting populations because of concerns that they birds would crowd out other colonial waterbirds.|
|Habitat||Coasts, bays, lakes, rivers. Very adaptable, may be found in almost any aquatic habitat, from rocky northern coasts to mangrove swamps to large reservoirs to small inland ponds. Nests in trees near or over water, on sea cliffs, or on ground on islands.|
Forages mostly by diving from surface and swimming underwater, propelled by feet (may sometimes use wings as well). May forage singly or in groups. May forage in clear or muddy water, at mid to upper levels of water more often than near bottom.
3-4, sometimes 1-7. Bluish white, becoming nest-stained. Incubation is by both sexes, 25-33 days, typically 28-30. Young: both parents feed the nestlings. After 3-4 weeks, young may leave ground nests and wander through colony, but return to nest to be fed. Usually first fly at about 5-6 weeks, probably independent at 9-10 weeks.
both parents feed the nestlings. After 3-4 weeks, young may leave ground nests and wander through colony, but return to nest to be fed. Usually first fly at about 5-6 weeks, probably independent at 9-10 weeks.
Fish and other aquatic life. Diet varies with season and place, includes very wide variety of fish, also crabs, shrimp, crayfish, frogs, salamanders, eels; sometimes snakes, mollusks, plant material.
Usually first breeds at age of 3 years. Nests in colonies, sometimes mixed with wading birds and others. Male displays to female on water by splashing with wings, swimming in zigzags, diving and bringing up pieces of weeds. At nest site, male displays by crouching and vibrating wings while calling. Nest: Site is near water on cliff ledge, on ground on island, or at any height in tree. Nest (built mostly by female, with materials brought by male) platform of sticks and debris, lined with finer materials.
Text © Kenn Kaufman, adapted from
Lives of North American Birds
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Some in Florida and on Pacific Coast may be permanent resident; most are migratory. Migrates in flocks, often following coastlines or rivers. Most travel probably by day.
- All Seasons - Common
- All Seasons - Uncommon
- Breeding - Common
- Breeding - Uncommon
- Winter - Common
- Winter - Uncommon
- Migration - Common
- Migration - Uncommon
See a fully interactive migration map for this species on the Bird Migration Explorer.Learn more
Songs and CallsDeep guttural grunts.
Learn more about this sound collection.