BREEDING BIOLOGY OF SECONDARY CAVITY-NESTING BIRDS IN OKLAHOMA

We examined reproductive success, nest failure, and timing of nest initiation for secondary cavity-nesting bird species in south-central Oklahoma. Habitats in study areas were old fields with patches of tallgrass prairie and fragments of oak woodland. By monitoring 150 nest boxes from 1989 to 1993, we studied a total of 334 nests, including those of Carolina chickadees (Parus carolinensis), tufted titmice (P. bicolor), Bewick's wrens (Thryomanes bewickii), eastern bluebirds (Sialia sialis), and house sparrows (Passer domesticus). Carolina chickadees and tufted titmice were single-brooded and nested early in the breeding season. The parids had the highest nesting success of the species studied. Nest initiations for eastern bluebirds extended from early March to late July, and eastern bluebirds were generally double-brooded and occasionally triple-brooded. Bewick's wrens and house sparrows had the lowest nesting success. Nest failures increased as the breeding season progressed primarily due to an increase in snake predation and nest abandonment. Except for bluebirds and house sparrows, interspecific competition for nest sites is unlikely given differences in habitat preferences and timings of nesting among the five species.