Estimating breeding season abundance of golden-cheeked warblers in Texas, USA
AuthorsMathewson, Heather A.
Groce, Julie E.
Mcfarland, Tiffany M.
Morrison, Michael L.
Newnam, J. Cal
Snelgrove, R. Todd
Collier, Bret A.
Wilkins, R. Neal
KAUST Grant NumberKUS-C1-016-04
Permanent link to this recordhttp://hdl.handle.net/10754/597971
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AbstractPopulation abundance estimates using predictive models are important for describing habitat use and responses to population-level impacts, evaluating conservation status of a species, and for establishing monitoring programs. The golden-cheeked warbler (Setophaga chrysoparia) is a neotropical migratory bird that was listed as federally endangered in 1990 because of threats related to loss and fragmentation of its woodland habitat. Since listing, abundance estimates for the species have mainly relied on localized population studies on public lands and qualitative-based methods. Our goal was to estimate breeding population size of male warblers using a predictive model based on metrics for patches of woodland habitat throughout the species' breeding range. We first conducted occupancy surveys to determine range-wide distribution. We then conducted standard point-count surveys on a subset of the initial sampling locations to estimate density of males. Mean observed patch-specific density was 0.23 males/ha (95% CI = 0.197-0.252, n = 301). We modeled the relationship between patch-specific density of males and woodland patch characteristics (size and landscape composition) and predicted patch occupancy. The probability of patch occupancy, derived from a model that used patch size and landscape composition as predictor variables while addressing effects of spatial relatedness, best predicted patch-specific density. We predicted patch-specific densities as a function of occupancy probability and estimated abundance of male warblers across 63,616 woodland patches accounting for 1.678 million ha of potential warbler habitat. Using a Monte Carlo simulation, our approach yielded a range-wide male warbler population estimate of 263,339 (95% CI: 223,927-302,620). Our results provide the first abundance estimate using habitat and count data from a sampling design focused on range-wide inference. Managers can use the resulting model as a tool to support conservation planning and guide recovery efforts. © 2012 The Wildlife Society.
CitationMathewson HA, Groce JE, Mcfarland TM, Morrison ML, Newnam JC, et al. (2012) Estimating breeding season abundance of golden-cheeked warblers in Texas, USA. The Journal of Wildlife Management 76: 1117–1128. Available: http://dx.doi.org/10.1002/jwmg.352.
SponsorsThe Texas Department of Transportation provided support for our work. Additionally, we acknowledge Texas Parks and Wildlife Department (TPWD) for support. We appreciate the private landowners who graciously allowed us access to their property, as well as TPWD, the U. S. Fish and Wildlife Service, The Nature Conservancy, City of Austin, Travis County, and the Lower Colorado River Authority. We thank J. Dunk, P. Hamel, R. Peak, W. Thogmartin, and F. Thompson III for helpful discussions regarding our research. We also thank J. Sedinger, B. Block, C. Farquhar, D. Wolfe, and numerous anonymous referees for insightful reviews on previous versions of this manuscript. We gratefully acknowledge A. Snelgrove, K. Skow, B. Stevener, and A. Dube for logistical support, as well as the many technicians and graduate students from Texas A&M University. B. A. Collier acknowledges partial support from Award No. KUS-C1-016-04 given by the King Abdullah University of Science and Technology (KAUST).