Papers in the Biological Sciences


Date of this Version

April 1987


From Diving Birds of North America (1987) by Paul A. Johnsgard. Copyright © 2007 Paul Johnsgard. Cite this work as: Paul Johnsgard, Diving Birds of North America (Lincoln, Nebraska: University of Nebraska Press, 1987; University of Nebraska–Lincoln Libraries, 2008 [ebook edition]).


Auks, loons, and grebes are birds whose anatomies and behaviors have been sharply influenced by their foraging niche adaptations. In each species these have evolved through natural selection over extended periods of geologic time as a reflection of available food resources, the presence of competing species, and the limitations on innate variations in anatomy, physiology, and behavior imposed by available genetic mutations and recombinations. To a very considerable degree the auks, loons, and grebes seem to have adjusted to the effects of interspecific competition by evolving differences in bill shape and body size that sometimes open specific new foraging niche opportunities to them and thus reduce direct competition with other species of their group.

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