The 12 species described in this volume are not closely related, but
they provide an instructive example of adaptive evolutionary radiation
within the much larger waterfowl lineage as to their divergent
morphologies, life histories, and social behaviors. The whistling-ducks
(Dendrocygna), with three known North American species, are notable for
their permanent pair-bonds, extended biparental family care, and strong
social cohesion. In contrast, males of the five typical pochards
(Aythya) maintain monogamous pair-bonds only long enough to assure that
the female's eggs are fertilized. The extreme of this behavior exists
among the stifftails (Oxyura). Such diverse reproductive strategies have
exerted powerful evolutionary influences on interspecies variations in
sexual dimorphism, sexual behavior, anatomy, ecology, and other traits.
This volume includes more than 63,000 words, plus some 200 maps, photos,
drawings, and sketches, and nearly 650 literature citations.