美洲骨顶种

The American coot is a migratory bird that occupies most of North America. It lives in the Pacific and southwestern United States and Mexico year-round and occupies more northeastern regions during the summer breeding season. In the winter they can be found as far south as Panama. Coots generally build floating nests and lay 8–12 eggs per clutch. Females and males have similar appearances, but they can be distinguished during aggressive displays by the larger ruff (head plumage) on the male. American coots eat primarily algae and other aquatic plants but also animals (both vertebrates and invertebrates) when available.

The American coot is closely related to the Eurasian coot (Fulica atra), which occupies the same ecological niche in Eurasia and Australia as the American coot does in North America. Eurasian coots can be distinguished from this species by the absence of a red callus above the bird's frontal shield.

The American coot is listed as "Least Concern" under the IUCN conservation ratings. Hunters generally avoid killing American coots because their meat is not as sought after as that of ducks.

American coots display several interesting breeding habits; mothers will preferentially feed offspring with the brightest plume feathers, which has resulted in coot chicks having brightly ornamented plumage which becomes drabber as they age. American coots are also susceptible to conspecific brood parasitism and have evolved mechanisms to differentiate their offspring from those of parasitic females.

Taxonomy and systematics

The American coot was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with all the other coots in the genus Fulica and coined the binomial name Fulica americana. Gmelin based his description on the "Cinereous coot" from North America that had been described in 1785 by the English ornithologist John Latham in his book A General Synopsis of Birds.

The American coot's genus name, Fulica, is a direct borrowing of the Latin word for "coot". The specific epithet americana means "America".

Subspecies

Two subspecies are recognised:

F. a. americana Gmelin, JF, 1789 – southeast Alaska and Canada to Costa Rica and the West Indies

F. a. columbiana Chapman, 1914 – Colombia and north Ecuador

Description

The American coot measures 34–43 cm (13–17 in) in length with a wingspan of 58 to 71 cm (23 to 28 in). Adults have a short, thick, white bill and white frontal shield, which usually has a reddish-brown spot near the top of the bill between the eyes. Males and females look alike, but females are smaller. Body mass in females ranges from 427 to 628 g (0.941 to 1.385 lb) and in males from 576 to 848 g (1.270 to 1.870 lb). Juvenile birds have olive-brown crowns and a gray body. They become adult-colored around 4 months of age.

Frontal shield and callus

The American coot is recognized by its white frontal shield with a red spot connecting its eyes. The size of the frontal shield depends on season and mating status. During the winter season, birds have smaller, 'shrunken' shields.

Distribution and habitat

American coots are found near water reed-ringed lakes and ponds, open marshes, and sluggish rivers. They prefer freshwater environments but may temporarily live in saltwater environments during the winter months.

The American coot's breeding habitat extends from marshes in southern Quebec to the Pacific coast of North America and as far south as northern South America. Birds from temperate North America east of the Rocky Mountains migrate to the southern United States and southern British Columbia. It is often a year-round resident where water remains open in winter. The number of birds that stay year-round near the northern limit of the species' range seems to be increasing.

Autumn migration occurs from August to December, with males and non-breeders moving south before the females and juveniles.

Behavior and ecology

The American coot is a highly gregarious species, particularly in the winter, when its flocks can number in the thousands. When swimming on the water surface, American coots exhibit a variety of interesting collective formations, including single-file lines, high density synchronized swimming and rotational dynamics, broad arcing formations, and sequential take-off dynamics.

Feeding

The American coot can dive for food but can also forage and scavenge on land. Their principal source of food is aquatic vegetation, especially algae. Yet they are omnivorous, also eating arthropods, fish, and other aquatic animals. During breeding season, coots are more likely to eat aquatic insects and mollusks—which constitute the majority of a chick's diet.

Predation

The American coot is fairly aggressive in defense of its eggs and, in combination with their protected nesting habitat, undoubtedly helps reduce losses of eggs and young to all but the most determined and effective predators. American crows, black-billed magpies and Forster's tern can sometimes take eggs. Mammalian predators (including red foxes, coyotes, skunks and raccoons) are even less likely to predate coot nests, though nests are regularly destroyed in usurpation by muskrats. Conversely, the bold behavior of immature and adult coots leads to them falling prey with relative regularity once out of the breeding season. Regular, non-nesting-season predators include great horned owls, northern harriers, bald eagles, golden eagles, American alligators, bobcats, great black-backed and California gulls.

In culture

On the Louisiana coast, the Cajun word for coot is pouldeau, from French for "coot", poule d'eau – literally "water hen". Coot can be used for cooking; it is somewhat popular in Cajun cuisine, for instance as an ingredient for gumbos cooked at home by duck hunters.

The bird is the mascot of the Toledo Mud Hens Minor League Baseball team.

Conservation and threats

The American coot is listed under "least concern" by the IUCN Red List of Endangered Species. They are common and widespread, and are sometimes even considered a pest. They are rarely the targets of hunters since their meat is not considered to be as good as that of ducks; although some are shot for sport, particularly in the southeastern United States. Because they are found in wetlands, scientists use them to monitor toxin levels and pollution problems in these environments.