Introduction

Probably the least-studied corvid in North America, the Chihuahuan Raven deserves increased attention. Initial research suggests it is just as interesting as the other species in this group. Intermediate in almost all overt characteristics between the American Crow (C. brachyrynchos) and the Common Raven (C. corax), it is easily confused with these 2 species. This raven occupies a limited range in desert regions of southwestern North America, its black color striking a stark contrast to the scorched, sun-baked and seemingly barren habitat that supports it. Indeed, the Chihuahuan Raven represents the epitome of a counterintuitive adaptation—dark plumage in a desert-dwelling bird. In addition to this bird’s glossy-black plumage, its most notable physical feature is the snow-white feathers underlying its neck—seen only when the wind ruffles its plumage or when an individual intentionally erects its feathers during social interactions.

This is an extremely social bird, but little of its social biology and the possible factors leading to its gregarious nature are available in the literature. It is social during all seasons, although pairs segregate somewhat during the early nesting season; nests tend to occur in clumps (3–5 nests in 1 area), normally separated by at least a few hundred meters. Whether this clumping is a function of available nest substrates or is integral to the breeding ecology of this species is unknown. Small groups of Chihuahuan Ravens are known to defend individual nests communally, sug-gesting some affiliation between adjacent breeders. As nesting dim-inishes and summer progresses, these ravens roost together in groups of up to 500 individuals.

Groups become larger in fall and winter and congregate in agricultural areas, perhaps to exploit aggregated food sources more effectively.

There is a glaring lack of contemporary research on this bird. Much of this account, by necessity, relies on older, anecdotal literature, often incomplete in its descriptions of methodology. Despite some weaknesses by today’s standards, Aldous’s (1942) monograph represents an excellent autecological study of this species and provides the basis for much of this review. Other substantial contributions have been made by Hudson and Bernstein (1981, 1983), Mishaga and Whitford (1983), and Haydock and Ligon (1986) on the energy cost of flight, development and heat balance of juveniles, and on factors influencing brood reduction, respectively. Much remains to be learned about this species, however.