American Coots

photo by Rohan Kamath
American Coots are noted for many qualities, some considerably less redeeming than others. Conspicuous, noisy, and aggressively territorial, they select from a repertoire of some 14 displays to communicate among themselves. To signal their social intentions coots vary body postures, adjust the position of the white undertail coverts, alter the degree to which they arch the wings over the back, change the angle of erect neck feathers and, when aroused, swell the frontal "nose" shield.

Many coot displays are associated with strident, year-long territorial defense. Generally, it is the male that confronts perceived threats. When the male partner is absent however, the female becomes demonstrative, reacting first to intruding
females before confronting intruding males. When an intruder appears, the resident approaches it by modifying its normal slow paddling into a hastened patrol swim and then makes a wake-forming charge that may end in a splattering, rapid run across the surface. Such confrontations may lead to combat. While fighting, a coot usually sits back on the water and grabs its opponent with one long-clawed foot while attempting to slap the contender with the free one and jab it with its bill. Apparently, the aim is to push the opponent onto its back and, in some cases, hold it underwater. Quite impressive, this sequence can be seen in coots four days old.

Not all displays directed toward unfamiliar coots are antagonistic, however. Coots communicate distress to each other by exposing their undertail coverts or displaying a swollen shield when alarmed by potential dangers such as hawks, airplanes, or predatory mammals. Similarly, aggressive displays are not restricted to avian intruders. If approached or harassed by other vertebrates, including people, coots will assert themselves by erecting their feathers so that they appear larger than life. Interestingly, coots do not perform distraction displays, even though Clappers and other rails do.

Not only are coots demonstrative, they are also hardy. For example, they can adjust well to hot temperatures. They have lobed feet, unique among gallinules, which, in addition to their use in battle, can effectively conduct heat out of the body. By immersing their feet in water, European Coots were able to tremendously increase their rate of heat loss and very quickly cool down when experimentally subjected to a temperature increase from 50 degrees to 104 degrees F.

American Coots are opportunistic feeders. In addition to hunting for themselves, however, they also feed commensally by taking leftovers from other species such as dabbling ducks, or they pirate plants brought to the surface by diving ducks such as Canvasbacks. Young coots are opportunistic as well. Groups of up to five juveniles may pirate aquatic vegetation from the bills of ducks and swans.

Overall, coot breeding behavior is not unlike other rails. Coots select breeding areas rich in nesting materials and build up to nine bulky, floating structures. They lay eggs in only one or two of them; the others are used for displaying, copulating, or brooding. Since incubation is not initiated until the fourth or fifth egg is laid, ample time is available beforehand for other birds to parasitize the clutch. But, American Coots, unlike the even more aggressive South American Red-fronted Coots, rarely host the eggs of other species. Redheads and Ruddy Ducks, the two common brood parasitic waterfowl in North America, reputedly ignore the very abundant American Coot nests. Ornithologist Milton Weller tried an experiment to find out why. Weller inserted chicken eggs into 43 coot nests at varying stages of nesting. The reason for the 100 percent failure of these eggs could not be pinpointed, but it appears that coots have somehow evolved a way to circumvent brood parasitism that requires neither the vigilance nor concerted effort seen in many other species.

Coots are among the least graceful of marsh birds. Commonly called "splatterers," they scramble across the surface of the water with wings flapping not only to confront intruders but also to become airborne. Coots bob their heads while walking, quite likely because the head movements help them to judge the distance to their prey. While foraging on insects, they bob quickly; while eating greens, they bob slowly. Appearing somewhat like aquatic pigeons, coots also bob their heads while swimming.

Since coots appear neither comical, vulnerable, nor inspirational, the public is often unsympathetic to their problems. American Coot flocks may number up to 1,500 individuals and the birds may readily attain pest status. In 1986, for example, employees at a California golf course shot 400 coots in an effort to keep them off the grass. Apparently their droppings accumulated on the putting greens and resulted in raised golf scores and tempers. But when coots disappear, they usually toll the bell for other species as well. In Hawaii, for example, where coot numbers were reduced to 1,500 by the mid-1970s and the island population was considered endangered, their decline was also an indicator of the rapid disappearance of island wetlands, an important habitat for many other Hawaiian species.
SEE: Brood Parasitism; Piracy; Temperature Regulation and Behavior; Thin as a Rail
Copyright ® 1988 by Paul R. Ehrlich, David S. Dobkin, and Darryl Wheye.