The American coot (Fulica americana), 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. or rafts. American coots eat primarily algae and other aquatic plants but also animals (both vertebrates and invertebrates) when available. American coots are also susceptible to conspecific brood parasitism and have evolved mechanisms to differentiate their offspring from those of parasitic females. 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

The Caribbean coot, a color morph of the American coot is now included with the nominate subspecies.<!--NACC 2016-A-9 -->

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 (formerly F. minor), famously known as part of the Fossil Lake fauna, quite possibly was a paleosubspecies of the American coot (as Fulica americana shufeldti) 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. Juvenile birds have olive-brown crowns and a gray body. They become adult-colored around 4 months of age.

Distribution and habitat

thumb|The American coot is regularly found in sizable flocks.

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.

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. 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.

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. 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. 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.thumb|American coot skeleton ([[Museum of Osteology)]]

Incubation and hatching

Incubation start time in the American coot is variable, and can begin anywhere from the deposition of the first egg to after the clutch is fully deposited. Starting incubation before the entire clutch has been laid is an uncommon practice among birds. Once incubation starts it continues without interruption. Male and female coots share incubation responsibility, but males do most of the work during the 21-day incubation period. Females will begin to re-nest clutches in an average of six days if clutches are destroyed during incubation.

Maternal effects

Hormones that are passed down from the mother into the egg affect offspring growth, behavior, and social interactions. These nongenetic contributions by the mother are known as maternal effects. In the American coot, two levels of androgen and testosterone variation have been discovered—within-clutch and among-clutch variation. Within the same clutch, eggs laid earlier in the sequence have higher testosterone levels than eggs laid later in the sequence. Females that lay three clutches deposit more androgens into their yolks than females who lay only one or two clutches.

Brood parasitism

The American coot has a mixed reproductive strategy, and conspecific brood parasitism is a common alternative reproductive method. In one 4-year study, researchers found that 40% of nests were parasitized, and that 13% of all eggs were laid by females in nests that were not their own. Increasing reproductive success under social and ecological constraints is the primary reason for brood parasitism. Floater females without territories or nests use brood parasitism as their primary method of reproduction, if they breed at all. Other females may engage in brood parasitism if their partially complete clutches are destroyed. Conspecific brood parasitic behavior is most common among females trying to increase their total number of offspring. Food supply is the limiting factor to chick survival and starvation is the most common cause of chick morbidity. Parasitic females bypass the parental care constraint of feeding by laying additional parasitic eggs in addition to their normal nest.

The American coot, unlike other parasitized species, has the ability to recognize and reject conspecific parasitic chicks from their brood. Parents aggressively reject parasite chicks by pecking them vigorously, drowning them, preventing them from entering the nest, etc. They learn to recognize their own chicks by imprinting on cues from the first chick that hatches. The first-hatched chick is a reference to which parents discriminate between later-hatched chicks. Chicks that do not match the imprinted cues are then recognized as parasite chicks and are rejected. Black American coot chicks have conspicuously orange-tipped ornamental plumes covering the front half of their body that are known as "chick ornaments" that eventually get bleached out after six days. This brightly colored, exaggerated trait makes coot chicks more susceptible to predation and does not aid in thermoregulation, but remains selected for by parental choice. These plumes are not necessary for chick viability, but increased chick ornamentation increases the likelihood that a chick will be chosen as a favorite by the parents. Experimental manipulation of chick ornamentation by clipping the bright plumes has shown that parents prefer ornamented chicks over non-ornamented ones.

In culture

thumb|1835 illustration by [[John James Audubon|J. J. Audubon]]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.thumb|Waddling in a marshy area

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.

References

Cited sources

  • American Coot – Fulica americana – USGS Patuxent Bird Identification InfoCenter.
  • American Coot Species Account – Cornell Lab of Ornithology