Coot hatching order tells identity.

The article discusses a report in the December 16, 2009 online issue of "Nature" showing that American coots have the cognitive ability to discern between their own chicks and that of an impostor. Topics include an overview of brood parasitism, in which a bird puts their eggs into the nest of another bird, how parasitic birds are able to match the host's egg color and patterning, and a theory on why evolution has not produced a sophisticated recognition of chicks.