I spent 2.5 years at North Carolina State University where I earned my MS in Fisheries, Wildlife, & Conservation Biology under the supervision of Dr. Chris Moorman. During that time I studied the breeding ecology of Bachman’s sparrows (Peucaea aestivalis) in North Carolina. Bachman’s sparrows are enigmatic residents of fire-maintained open-pine ecosystems in the Southeast, and the species has been declining in response to fire-suppression and the extensive loss (~97%) of longleaf pine (Pinus palustris) ecosystems. Consequently, Bachman’s sparrow is listed as a species of conservation concern across its range, but demographic mechanisms underlying declines and many aspects of its natural history remain poorly understood. To address these knowledge gaps, I investigated reproductive success, space-use, and habitat selection of Bachman’s sparrows across a fragmentation gradient in the Coastal Plain of North Carolina.
Nesting ecology of Bachman’s sparrows in different longleaf pine communities
Understanding aspects of Bachman’s sparrow breeding biology may provide valuable insights into population declines and inform restoration and management of remnant longleaf pine habitats, but factors such as nest-site selection and nest survival have received little attention due to difficulty in locating the species’ cryptic nests. We investigated spatial variation in the nesting ecology of Bachman’s sparrows in two distinct longleaf pine communities occurring in the Coastal Plain and Sandhills physiographic regions of south-central North Carolina. Our collaborative study (NC State University, NC Wildlife Resources Commission, and Dept. of Defense) from concurrent research in these two regions used the largest dataset of nests collected to date for this species (N = 132 nests). For each region, we modeled nest-site selection and nest survival as a function of vegetation characteristics, burn history, temporal factors, and landscape-level habitat amount. We found that there were distinct differences in nest-site selection among regions, with Bachman’s sparrows in the Coastal Plain region selecting greater woody vegetation density and lower grass density at nest sites than at non-nest locations. Conversely, sparrows selected nest sites with intermediate grass density and higher tree basal area in the Sandhills. Despite clear patterns of nest-site selection, we detected no predictors of nest survival in the Sandhills, and nest survival only varied with date in the Coastal Plain. Daily survival rates were similar between regions, and were consistent with published studies from the species’ core range where declines are less severe. Overall, our results indicate that creating and maintaining community-specific vegetation characteristics through the application of frequent prescribed fire should increase the amount of nesting cover for Bachman’s sparrow.
Winiarski, J. M., A. C. Fish, C. E. Moorman, J. P. Carpenter, C. S. DePerno, and J. M. Schillaci. 2017. Nest-site selection and nest survival of Bachman’s Sparrows in two longleaf pine communities. The Condor: Ornithological Applications 119:361–374.
Check out the press release for the paper here!
Reproductive consequences of habitat loss and fragmentation
Habitat loss and fragmentation are major threats to bird population persistence. Yet, our understanding of the demographic factors behind the adverse effects of fragmentation remains limited for many species, including the Bachman’s sparrow. We quantified the effects of local- and landscape-scale factors on different components of reproductive success (i.e., pairing success and probability of fledging offspring) for 96 male sparrows at eight sites in southeastern North Carolina. Pairing success of monitored sparrows was 69%, and 77% of paired males fledged ≥1 offspring. Habitat amount in the surrounding landscape, rather than local habitat quality, was the most influential predictor of pairing success for male Bachman’s sparrows. In contrast, we documented no predictors of successfully fledging offspring for paired males. We infer that reduced pairing success is limiting reproduction in isolated landscapes and may be a contributing factor for the low occupancy and declines of Bachman’s sparrow in our study region. Overall, our results suggest that managers can promote breeding opportunities for Bachman’s sparrows by prioritizing resources to patches near large, preexisting longleaf pine forest to ensure ≥20% habitat within the surrounding landscape.
Winiarski, J. M., C. E. Moorman, J. P. Carpenter, and G. R. Hess. 2017. Reproductive consequences of habitat fragmentation for a declining resident bird of the longleaf pine ecosystem. Ecosphere 8(7):e01898. 10.1002/ecs2.1898.
Bachman’s sparrow home range size and microhabitat selection at the northern periphery of the species’ range
Bachman’s sparrows have declined range-wide since the late 1960s, with peripheral populations exhibiting some of the steepest declines. For example, the species is now rare or extirpated over much of the northern extent of its historical range (e.g., Virginia and much of North Carolina). To better understand the spatial ecology of Bachman’s sparrows in this region of decline, we examined microhabitat selection and determined the home range sizes of radio-tagged male Bachman’s sparrows. From April to July, we located males 1–2 times daily for 5–6 days per week, and measured vegetation structure at telemetry locations and available unused locations within home ranges. Mean home range size (7.9 ha) was larger than estimates reported in most previous studies, with variation among studies possibly due to differences in habitats and methodology. Bachman’s sparrows in our study showed clear selection for several vegetation characteristics linked to frequent fire, and management strategies that approximate historical fire regimes in longleaf pine ecosystems should continue to be promoted as essential tools for the conservation of Bachman’s sparrows.
Winiarski, J. M., C. E. Moorman, and J. P. Carpenter. 2017. Bachman’s Sparrows at the northern periphery of their range: home range size and microhabitat selection. Journal of Field Ornithology 88:250-261.