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.