Cost-Distance Analysis of Connectivity for an Avian Migrant Inhabiting a Fragmented Network
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Dispersal is key to the persistence of metapopulations and local populations. The Black-capped Vireo (Vireo atricapilla, hereafter BCVI) is an endangered Neotropical migrant that breeds in discrete patches of shrubland. On the Edwards Plateau a patchwork of this habitat is maintained through periodic disturbance. I applied a cost-distance scenario based on the amount of woody cover, level of human presence, and local topography, to a series of classified landcover maps of the Balcones Canyonlands region of central Texas to determine whether a cost distance model fit observed levels of dispersal of BCVI better than simple geographic (Euclidean) distance. Pair-wise connectivity values for a set of habitat patches on the Balcones Canyonlands Preserve (BCP) and Balcones National Wildlife Refuge (BCNWR) were evaluated for the 2008-2009 breeding seasons via a program of color-banding and resighting. Interpatch exchange rates were converted to measures of dissimilarity, entered into a pattern matrix, and confronted to model matrices containing effective distance values generated by cost-distance analysis, using simple and partial Mantel tests. Although statistical power was limited because of small sample size (n = 4), results provide weak support for the continued use of geographic distance as a metric for interpatch connectivity.