title: Quantifying the importance of patch-specific changes in habitat to metapopulation viability of an endangered songbird.
abstract: A growing number of programs seek to facilitate species conservation using incentive-based mechanisms. Recently, a market-based incentive program for the federally endangered Golden-cheeked Warbler (Dendroica chrysoparia) was implemented on a trial basis at Fort Hood, an Army training post in Texas, USA. Under this program, recovery credits accumulated by Fort Hood through contracts with private landowners are used to offset unintentional loss of breeding habitat of Golden-cheeked Warblers within the installation. Critical to successful implementation of such programs is the ability to value, in terms of changes to overall species viability, both habitat loss and habitat restoration or protection. In this study, we sought to answer two fundamental questions: Given the same amount of change in breeding habitat, does the change in some patches have a greater effect on metapopulation persistence than others? And if so, can characteristics of a patch (e.g., size or spatial location) be used to predict how the metapopulation will respond to these changes? To answer these questions, we describe an approach for using sensitivity analysis of a metapopulation projection model to predict how changes to specific habitat patches would affect species viability. We used a stochastic, discrete-time projection model based on stage-specific estimates of survival and fecundity, as well as various assumptions about dispersal among populations. To assess a particular patch's leverage, we quantified how much metapopulation viability was expected to change in response to changing the size of that patch. We then related original patch size and distance from the largest patch to each patch's leverage to determine if general patch characteristics could be used to develop guidelines for valuing changes to patches within a metapopulation. We found that both the characteristic that best predicted patch leverage and the magnitude of the relationship changed under different model scenarios. Thus, we were unable to find a consistent set of relationships, and therefore we emphasize the dangers in relying on general guidelines to assess patch value. Instead, we provide an approach that can be used to quantitatively evaluate patch value and identify critical needs for future research.
authors.affiliation: Department of Fish and Wildlife Resources, University of Idaho, P.O. Box 441136, Moscow, Idaho 83844-1136, USA. jhorne@uidaho.edu
authors.forename: Jon S
authors.initials: JS
authors.lastname: Horne
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Strickler
authors.forename: Mathew
authors.initials: M
authors.lastname: Alldredge
mesh_terms: D000818:Animals; D017753:Ecosystem; D056727:Endangered Species; D008954:Models, Biological; D011157:Population Dynamics; D020308:Songbirds / Q000502:physiology*