Common Raven (Corvus corax) numbers in the Mojave Desert have grown substantially, with increases ranging from 5 to 15% annually over the past 20 years (Robbins et al. 1986, USDI 1990). These population increases, and the location of Desert Tortoise (Gopherus agassizii) shells near raven nests and perches, have resulted in ravens being suggested as a cause of the decline of tortoise populations (Berry 1985, Berry et al. 1986).
The conclusion that raven populations have increased is based on Breeding Bird Surveys, in which birds are counted from roadsides (Robbins et al. 1986). Estimates of raven populations are thus based on data from areas of diverse human land uses including agriculture, livestock grazing, and urban/suburban development. Knight and Kawashima (in press), however, found that raven numbers can be considerably greater along highways than away from them. Currently, there is no information on raven numbers in areas away from roads and not grazed by livestock.
Accordingly, we surveyed raven numbers in native desert scrub away from roads. Our goal was to determine a baseline estimate of raven population density in a part of the Mojave Desert suitable for nesting ravens but free from contemporary land-use changes.