Demographic and behavioral responses of permanent-resident cavity-nesting birds to forest fragmentation and West Nile virus.

摘要

I related environmental parameters to the demographics of permanent resident avian cavity nesters in Crawford County, OH. I also examined how demographic parameters of Carolina chickadees (Poecile carolinensis) supported or refuted source/sink, site-dependent regulation, and metapopulation models. With the arrival of West Nile virus (WNV), I collected blood from selected avian species during 2002-2005 and found no chickadees tested positive for WNV antibodies, while northern cardinals (Cardinalis cardinalis) and eastern screech owls (Megascops asio) had the largest proportion of individuals testing positive for WNV antibodies. Individuals of some species were found to lose their antibodies over time.; Differences in seroprevalence of Carolina chickadees and northern cardinals prompted an experiment to determine if such differences could be the result of antimosquito behavior by birds. No differences were detected in the ability of Carolina chickadees and northern cardinals to prevent mosquitoes from taking blood meals.; Two demographic parameters measured were reproductive success and annual survival. Reproductive success of Carolina chickadees nesting in natural cavities and house wren (Troglodytes aedon) abundance increased and decreased, respectively, with woodlot area. Mammalian predation was unrelated to woodlot area, so house wrens appeared to be the primary reason for differences in chickadee reproductive success related to woodlot area.; Survival varied among years in Carolina chickadees and tufted titmice (Baeolophus bicolor), but was constant in white-breasted nuthatches (Sitta carolinensis) and downy woodpeckers ( Picoides pubescens) over the study period, 1994-2005. Although it is difficult to determine how much impact WNV had on survival, of these four species, the virus may have had the greatest impact on tufted titmice. Winter severity appeared to be important for Carolina chickadee survival, while no models were useful in explaining tufted titmouse survival. White-breasted nuthatch survival was higher in isolated woodlots than in riparian sites, while downy woodpecker survival increased with woodlot area and was highest in riparian sites. Eastern screech owl (Megascops asio) survival appeared to be greatly influenced by WNV. Owls banded prior to the WNV outbreak in 2002 were never captured again. After 2002, screech owl survival steadily increased and, by 2006, had reached pre-WNV levels.; Finally, I matched various characteristics of the Carolina chickadee population to predicted results of source/sink, site-dependent regulation, and metapopulation models. Habitat quality varied among sites and appeared to be an important factor determining chickadee presence. Site-dependent regulation was the best-supported model, although not all predictions of that model were supported. Chickadees do not appear to select sites based solely on habitat quality as I measured it, indicating that site selection may be a more complicated process.