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Western Grebe
Aechmophorus occidentalis
Order
PODICIPEDIFORMES
– Family
PODICIPEDIDAE
Authors: Storer, R. W., and G. L. Nuechterlein
Revisors: LaPorte, Nicholas

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Introduction

Breeding adult Western Grebe, Moss Landing, CA, 27 March.
Figure 1. Distribution of the Western and Clark's Grebe, whose ranges overlap.

The Western and Clark’s grebes are conspicuous water birds of western North America, from southern Canada to the Mexican Plateau. They are perhaps best known for their elaborate and energetic courtship rituals, now well-studied.  These courtship ceremonies -- in which these birds perform a series of displays in ritualized, apparently mechanical, sequences -- are among the most complex known in birds.

Perhaps even more remarkable is the fact that, with one exception, the rituals of these two species are identical. The exception is the number of notes, one or two, in the Advertising call; yet this, plus differences in bill color and facial pattern, are enough for individuals to recognize birds of their own species and to choose them as mates. Discovery of this preferential mating led to several valuable studies of the degree of relationship between the two forms and to their recognition as distinct species rather than color phases of the same species.

Western and Clark’s grebes are unique among grebes in possessing a mechanism in the neck that permits them to thrust forward the head like a spear. Such a mechanism is well known in herons and anhingas, but its details remain to be worked out in these grebes.

Because the Western and Clark’s grebes were considered color phases of one species—the Western Grebe—from 1886 until 1985, the literature on them was combined under that name. Only rarely was mention made of the “phase” of the birds studied. Because of this, and because of the great similarity between the two species in morphology and behavior, this account treats both species. First, under Western Grebe, is given the information known to apply to that species alone, that common to both species, and that for which the “phase” was not mentioned. The companion account of Clark’s Grebe (BNA account # xxx) consists of information known to apply to that species and to known differences between the two.

Although the behavior of the northern subspecies of these birds has been well studied, little is known of their longevity and movements, owing to a paucity of banding recoveries. Parallel studies on the biology of the Mexican races of these species could greatly aid our understanding of the evolution of these species.