BREEDING BIOLOGY OF SECONDARY CAVITY-NESTING BIRDS IN OKLAHOMA

We examined reproductive success, nest failure, and timing of nest ini tiation for secondary cavity-nesting bird species in south-central Okl ahoma. Habitats in study areas were old fields with patches of tallgra ss prairie and fragments of oak woodland. By monitoring 150 nest boxes from 1989 to 1993, we studied a total of 334 nests, including those o f Carolina chickadees (Parus carolinensis), tufted titmice (P. bicolor ), Bewick's wrens (Thryomanes bewickii), eastern bluebirds (Sialia sia lis), and house sparrows (Passer domesticus). Carolina chickadees and tufted titmice were single-brooded and nested early in the breeding se ason. The parids had the highest nesting success of the species studie d. Nest initiations for eastern bluebirds extended from early March to late July, and eastern bluebirds were generally double-brooded and oc casionally triple-brooded. Bewick's wrens and house sparrows had the l owest nesting success. Nest failures increased as the breeding season progressed primarily due to an increase in snake predation and nest ab andonment. Except for bluebirds and house sparrows, interspecific comp etition for nest sites is unlikely given differences in habitat prefer ences and timings of nesting among the five species.