#pouldeau

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 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. 

Much research has been done on the breeding habits of American coots. Studies have found that mothers will preferentially feed offspring with the brightest plume feathers, a characteristic known as chick ornaments.  The first evidence for parental selection of exaggerated, ornamental traits in offspring was found in American coots. 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.  

American coots are also susceptible to conspecific brood parasitism and have evolved mechanisms to identify which offspring are theirs and which are from parasitic females. 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. 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.