The Use of Prickly Pear Cactus as Nesting Cover by Northern Bobwhites

Years of research on the nesting ecology of the northern bobwhile (Colinus virginianus) have documented the use of bunchgrasses as common nesting cover. However, in the Rolling Plains of Texas, recent studies indicate a relatively high use of prickly pear cactus (Opuntia spp.) as suitable nesting cover. To explain this previously unreported use of prickly pear, we evaluated 2 hypotheses: (1) the limited-bunchgrass, and (2) nest-protection hypotheses. We speculated that bobwhites nested in prickly pear cactus because of low availability of bunchgrasses and/or structural protection against predators. We radioinarked 218 bobwhites during spring and summer of 1997 and 1998 on 4 sites in Shackelford County, Texas, USA. Bobwhites nested in prickly pear despite adequate bunchgrass cover (>600 potential nesting sites/ha). Of 81 nests located, 12% were in shrubs (e.g., catclaw [Acacia greggii]), 30% were in prickly pear, and 58% were in bunchgrass. Nest success did not differ among nesting substrates (X 2 = 2.1, df= 2, P= 0.35) but was dependent on the degree of protection provided by the nesting substrate (X 2 = 16, df= 2, P= 0.001). However, successful nests also had a higher density of bunchgrasses in the surrounding arca than unsuccessful nests (P = 0.001). Our data partially supported the nest-protection hypothesis and did not support the limited-bunchgrass hypothesis.