http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
value of prickly pear cactus as nesting cover for northern bobwhite
xiii, 85 leaves : illustrations, maps ; 28 cm.
Habitat changes at the landscape level have been cited as a primary cause in the decline of northern bobwhite (Colinus virginianus) populations. Because prickly pear cactus (Opuntia spp.) has invaded millions of hectares of Texas rangeland, prickly pear control through prescribed fire and subsequent aerial spraying of the herbicide picloram has become a common practice in the Rolling Plains. My objectives were to compare: (1) bobwhite survival in treated (burned and picloram sprayed; 3-5 years post treatment) and untreated sites; (2) nest success between nests in prickly pear or bunchgrass habitat; (3) operative temperatures between simulated bobwhite nests located in prickly pear or bunchgrass habitat; and, (4) nest success between actual nests and simulated ("dummy'') nests. I radio-marked 218 bobwhites at 4 private ranches (each with a treated and untreated site) in Shackelford County, Texas from March-August 1997-98. Within this study area, microclimate data were collected at simulated bobwhite nests located in prickly pear or bunchgrass habitat. Also, after an actual nest was depredated or successful, simulated nests were placed in the vicinity of actual nests. There was no difference in bobwhite survival between treated and untreated sites (P > 0.10) or nest success between nest habitats (P = 0.35). I observed no difference in operative temperature between simulated bobwhite nests in prickly pear or bunchgrass habitat, except in June 1997 (P = 0.02). There was no difference in nest success between actual and simulated nests (P > 0.20). Under the conditions of my study, prickly pear control does not appear to affect bobwhite survival 3-5 years post treatment. This may be explained by stocking density and age of treatment. Factors other than nest habitat alone (e.g., degree of mechanical protection offered by prickly pear, bunchgrass density) may influence nest success. Also, operative temperature may not adequately explain the use of prickly pear as a nesting substrate. A more plausible explanation may be prickly pear serves as a nest predator deterrent. Lastly, simulated nests may provide useful trend data of actual bobwhite nest success.
Issued also on microfiche from University Microfilm Inc.
Includes bibliographical references (leaves 67-79).