Determinants of nest survival in a managed Florida Scrub-Jay population

Abstract

Bird populations occupying managed transitional habitats often have low nest success because optimal habitat conditions are not maintained. In such cases, quantifying determinants of nest survival provides information for habitat maintenance or restoration. Our goal was to determine the current factors affecting nest survival in a managed but declining population of the Florida Scrub-Jay (Aphelocoma coerulescens) in Merritt Island National Wildlife Refuge. We used an information-theoretic approach and nest-survival models in program MARK to test a priori hypotheses for survival of Florida Scrub-Jay nests. Failure of Florida Scrub-Jay nests was common; only 35% of 614 were successful in producing at least one fledgling. Ninety-four percent of 399 nest failures were due to predation. Nest survival was highest in oak-dominated territories, varied by population center, and decreased with proximity to forest edges, as the season progressed, and with increasing accumulated rainfall prior to the nesting season. Shrub height, a primary focus of current efforts at habitat-quality assessment and management, was not well supported as a determinant of survival of Florida Scrub-Jay nests at Merritt Island. We suggest hypotheses to explain the lack of support for an effect of shrub height, and we conclude that mitigation of low nest survival at Merritt Island may require additional actions. © The Cooper Ornithological Society 2011.