The use of prickly pear cactus as nesting cover by northern bobwhites
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abstract
Years of research on the nesting ecology of the northern bobwhite ( 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 radiomarked 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 (2 = 2.1, df = 2, P = 0.35) but was dependent on the degree of protection provided by the nesting substrate (2 = 16, df = 2, P = 0.001). However, successful nests also had a higher density of bunchgrasses in the surrounding area than unsuccessful nests (P = 0.001). Our data partially supported the nest-protection hypothesis and did not support the limited-bunchgrass hypothesis.
