Plumage maturation, molt, and morphology of the critically endangered Hooded Grebe (<i>Podiceps gallardoi</i>)

The understanding of morphological and behavioral aspects of bird species can guide appropriate management actions for their conservation. Grebes (Podicipedidae) are peculiar in their molting strategy, since body feathers are continuously replaced during the whole year. Available information about natural history of Neotropical grebes is scattered. The Hooded Grebe (Podiceps gallardoi) is a critically endangered species with a global population of less than 800 individuals that inhabits the remote highlands plateaus of Austral Patagonia. In this work we present information about sexual differences in molting behavior, plumage coloration and morphological characteristics of this species. During seven years we monitored the whole population of Hooded Grebe and collected data from field observations and from collected individuals that had been killed by American mink. Our results show sexual differences in morphology, and in timing of molting, but not in coloration in the UV and visible range. Hooded Grebe’s molting strategy differs from that of other grebes, including closely related species, as it lacks molting migration and does not develop a visibly different alternate winter plumage. Molting strategies and morphological differences between sexes may represent adaptations to variable conditions in extreme environments of southern Patagonia.