American coot
The American coot, also known as a mud hen or pouldeau, is a bird of the family Rallidae. Though commonly mistaken for ducks, American coots are only distantly related to ducks, belonging to a separate order. Unlike the webbed feet of ducks, coots have broad, lobed scales on their lower legs and toes that fold back with each step to facilitate walking on dry land. Coots live near water, typically inhabiting wetlands and open water bodies in North America. Groups of coots are called covers or rafts. The oldest known coot lived to be 22 years old.
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 on the male. American coots eat primarily algae and other aquatic plants but also animals when available.
The American coot is closely related to the Eurasian coot, 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.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
Fossil record
Coot fossils from the Middle Pleistocene of California have been described as Fulica hesterna but cannot be separated from the present-day American coot. However, the Pleistocene coot Fulica shufeldti, famously known as part of the Fossil Lake fauna, quite possibly was a paleosubspecies of the American coot as they only differed marginally in size and proportions from living birds. Thus, it seems that the modern-type American coots evolved during the mid-late Pleistocene, a few hundred thousand years ago.The American coot's genus name, Fulica, is a direct borrowing of the Latin word for "coot". The specific epithet americana means "America".
Description
The American coot measures in length with a wingspan of. 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 and in males from. 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. During breeding season, birds are recorded to have swelled shields. Birds that are permanently paired or mated have larger shields as well.According to a 1949 coverage by , the reddish-brown spot on the frontal shield is not considered a part of the frontal shield despite its proximity to the shield. It is known as the callus. This is due to the fact that it does not completely cover the maxilla, or jawbone, of the coot. It also differs in color and texture from the shield.
Vocalizations
The American coot has a variety of repeated calls and sounds. Male and female coots make different types of calls to similar situations. Male alarm calls are ' while female alarm calls are '. Also, stressed males go ' or ' while females call .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. Spring migration to breeding ranges occurs from late February to mid-May, with males and older birds moving North first. There has been evidence of birds travelling as far north as Greenland and Iceland.
Caribbean coot
Coots resident in the Caribbean and Greater and Lesser Antilles lack the red portion of the frontal shield, and were previously believed to be a distinct species, the Caribbean coot. In 2016, due to research showing that the only distinguishing characteristic between American and Caribbean coots, the presence or absence of red in the frontal shield, was not distinct to Caribbean coots as some American coots, in locations where vagrancy from Caribbean populations was highly unlikely, had fully white shields and, therefore, there was no way to reliably distinguish the species, and there was no evidence of Caribbean and American coots engaging in assortative mating, the American Ornithological Society lumped the Caribbean coot as a regional variation of the American coot.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.Breeding
The coot mating season occurs during May and June. Coot mate pairings are monogamous throughout their life, given they have a suitable territory. A typical reproductive cycle involves multiple stages: pairing, nesting, copulation, egg deposition, incubation, and hatching.The American coot typically has long courtship periods. This courtship period is characterized by billing, bowing, and nibbling. Males generally initiate billing, which is the touching of bills between individuals. As the pair bond becomes more evident, both males and females will initiate billing only with each other and not other males or females. After a pair bond is cemented, the mating pair looks for a territory to build a nest in. A pair bond becomes permanent when a nesting territory is secured. Copulation behavior among coot pairs always falls under the same general pattern. First the male chases the female. Then, the female moves to the display platform and squats with her head under the water. The male then mounts the female, using his claws and wings to balance on the female's back while she brings her head above the water. Sexual intercourse usually takes no longer than two seconds.
Nests
The American coot is a prolific builder and will create multiple structures during a single breeding season. It nests in well-concealed locations in tall reeds. There are three general types of structures: display platforms, egg nests and brood nests.- Display platforms are used as roosting sites and are left to decompose after copulation.
- Egg nests are typically in diameter with a ramp that allows the parents to enter and exit without tearing the sides of the nests. Coots will often build multiple egg nests before selecting one to lay their eggs in.
- Brood nests are nests that are either newly constructed or have been converted from old egg nests after the eggs hatch, becoming larger egg nests.
Egg-laying and clutch size
Females deposit one egg a day until the clutch is complete. Eggs are usually deposited between sunset and midnight. Typically, early season and first clutches average two more eggs than second nestings and late season clutches. Early season nests see an average of 9.0 eggs per clutch while late clutches see an average of 6.4 eggs per clutch. There is an inverse relationship between egg weights and laying sequence, wherein earlier eggs are larger than eggs laid later in the sequence. It is possible to induce a female coot to lay more eggs than normal by either removing all or part of her clutch. Sometimes, a female may abandon the clutch if enough eggs are removed. Coots, however, do not respond to experimental addition of eggs by laying fewer eggs.The American coot is a persistent re-nester, and will replace lost clutches with new ones within two days of clutch-loss during deposition. One study showed that 68% of destroyed clutches are eventually replaced. Re-nested clutches are typically smaller than original clutches by one or two eggs, but this could be attributed to differences in time and habitat quality instead of food or nutrient reserves and availability.
Younger females reproduce later in the season and produce smaller eggs than older females. Their offspring are also smaller. However, there is no difference in clutch size between older and younger females as there is in other avian species.