> >From http://www.ucsc.edu/news_events/press_releases/text.asp?pid=322
>
>SANTA CRUZ, CA--Coots, the Rodney Dangerfields of the bird world, just
>might start to get some respect as a result of a new study showing that
>these common marsh birds are able to recognize and count their own eggs,
>even in the presence of eggs laid by other birds.
>
>The counting ability of female coots is part of a sophisticated set of
>defense mechanisms used to thwart other coots who lay eggs in their
>neighbors' nests, according to Bruce Lyon, an assistant professor of
>ecology and evolutionary biology at the University of California, Santa
>Cruz. Lyon studied hundreds of coot nests in British Columbia during a
>four-year investigation. His latest findings appear in the April 3 issue
>of the scientific journal Nature.
>
>"The ability of females to count only their own eggs in a mixture of
>eggs is a remarkable feat that provides a convincing, rare example of
>counting in a wild animal," Lyon wrote in the published paper.
>
>A member of the rail family, the American coot (Fulica americana) is a
>slate-gray bird with a white beak, about the size of a small duck. It
>inhabits lakes, ponds, and marshes, often in large numbers. Coots
>are ungainly on land, reluctant to fly, and not very impressive in the
>water, either. Use of the word coot to mean a stupid person or simpleton
>reflects prevailing attitudes toward these rather comical birds. But this
>perception is belied by Lyon's discovery of their impressive cognitive
>abilities.
>
>"I was shocked. At first, I didn't believe the results," he said.
>
>Lyon originally set out to study how coot parents care for their
>chicks. But the focus of his research changed when he discovered extremely
>high levels of "brood parasitism," the practice of laying eggs in other
>birds' nests. Most studies of brood parasitism have looked at birds like
>cuckoos, which lay their eggs in other species' nests and thereby avoid
>the trouble of raising their own chicks. But brood parasitism also occurs
>within species, and Lyon's research on coots is shedding new light on
>this little-studied phenomenon.
>
>Lyon and his field assistants tracked the fate of every egg in more than
>400 coot nests, checking the nests every day. Because no bird can lay
>more than one egg per day, parasitism was readily detected. In addition,
>coot eggs laid by different parents can often be distinguished on the
>basis of color and speckle pattern.
>
>"The egg pattern is like a fingerprint," Lyon said. "It turns out that in
>most cases, the parasitism is done by females who have their own nests,
>and often it's the next-door neighbor, so by comparing the eggs in nearby
>nests we can tell who's doing it."
>
>Parasitism was rampant, affecting 41 percent of the nests and accounting
>for 13 percent of all the eggs laid in the study population. Furthermore,
>the cost of parasitism to the hosts was quite high.
>
>"There's not enough food for all the eggs that get laid, so there is
>a massive die-off of chicks. Typically about half the chicks in a nest
>starve to death," Lyon said. "That explains both the cost of parasitism
>to the host and the benefit to the parasite."
>
>Female coots, Lyon found, are quite good at recognizing and rejecting
>parasitic eggs. Rejected eggs were buried deep in the nesting material and
>never hatched. In some cases, parasitic eggs were not rejected outright,
>but were banished to inferior incubation positions, resulting in delayed
>hatching and decreased likelihood of survival for the parasitic chicks.
>
>"They may use that strategy to deal with eggs they are less certain of,"
>Lyon said. "It's subtle, but it has an effect on reproductive success,
>because the ones that hatch later are more likely to perish."
>
>Evidence that coots are able to count their eggs was completely
>unanticipated. Lyon wanted to look at how the presence of parasitic
>eggs affected clutch size. Coots are indeterminate layers, meaning
>that they'll keep laying eggs until an external cue tells them they're
>done. Speculation about the nature of the cue has long favored the
>sense of touch--when the female feels like she's sitting on the right
>number of eggs, the development of new egg follicles stops. (Follicles
>that have already started developing continue to develop, so there is
>a delay between the cue and the cessation of egg laying.)
>
>If the birds use a touch cue, the presence of parasitic eggs should
>cause a female to lay fewer of her own eggs. But Lyon found that when
>female coots recognized the parasitic eggs in their nests, eventually
>rejecting them, they did not reduce their clutch size. In contrast,
>females that failed to recognize parasitic eggs laid one fewer of their
>own eggs for each parasitic egg they received.
>
>"Rejection takes a long time, so the clutch-size decision is made while
>the parasitic eggs are still in the nest," Lyon said. "That means they
>are not using a touch cue. These birds are looking at their nests
>and counting only those eggs they recognize as their own to make a
>clutch-size decision."
>
>Lyon noted that the meaning of "counting" in animals is a highly
>contentious issue among cognitive psychologists and animal behavior
>experts. What he means by counting is that the birds are making decisions
>based on the number of eggs in their nests.
>
>"That's pretty amazing for a 'stupid' bird like a coot," Lyon said. "It's
>very satisfying to rescue a study animal from a bad rap."
>
>_____
>
>Note to reporters: You may contact Lyon at (831) 459-3949 or
>lyon at biology.ucsc.edu.
>
>Images can be downloaded from the web at
>http://www.ucsc.edu/news_events/download/.


--
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