Responses of small rodents to habitat restoration and management for the imperiled Florida Scrub-Jay

Debate about the relative merits of single-species management versus more comprehensive approaches has intensified in recent years. In east-central Florida, USA, land managers use prescribed burns and mechanical cutting to manage and restore scrub habitat to benefit the imperiled Florida Scrub-Jay (Aphelocoma coerulescens). However, these land-management techniques may affect non-target taxa, especially the threatened southeastern beach mouse (Peromyscus polionotus niveiventris). We evaluated the collateral effects of single-species land management by trapping P. p. niveiventris and other small rodents in eighteen land-management compartments at Cape Canaveral Air Force Station, Florida during 2004–2005. Compartments were managed using either prescribed burns (N = 5), mechanical cutting (N = 6), checkerboarding (cut and uncut lanes alternating and overlapping, followed by a prescribed burn, N = 4) or left unburned and uncut for >50 year (N = 3). P. p. niveiventris was significantly more abundant in compartments managed with prescribed burns (mean ± SE: 4.2 ± 0.7 individuals/transect) than those managed with cutting alone (1.0 ± 0.3) or not managed for >50 y (0.2 ± 0.1 individuals/transect). In contrast, the cotton mouse (Peromyscus gossypinus) tended to be more abundant in compartments managed with mechanical cutting alone (2.6 ± 0.4 individuals/transect) compared to the other three management strategies (prescribed burns; 1.5 ± 0.4; checkerboarding, 1.1 ± 0.3; not managed, 1.6 ± 0.4 individuals/transect) but these differences were not statistically significant. Abundances of P. p. niveiventris and Florida Scrub-Jay breeding groups were positively correlated (r = 0.655), suggesting that both listed species benefit from similar management techniques. Thus, the mosaic of burned and cut patches used to improve habitat for the Florida Scrub-Jay also benefits an endemic, non-target species. Single-species management may benefit multiple species when restoration improves their shared habitat, which in this case is an endangered, fire-dependent ecosystem: Florida scrub.     

Using landscape metrics to model source habitat for Neotropical migrants in the midwestern U.S.

Size of a forest patch is a useful predictor of density and reproductive success of Neotropical migratory birds in much of eastern North America. Within these forested landscapes, large forest tracts appear to be sources – fragments in which surpluses of offspring are produced and can potentially colonize new fragments including woodlot sinks where reproduction fails to balance adult mortality. Within agricultural landscapes of the midwestern U.S., where forests are severely fragmented, high levels of brood parasitism by brown-headed cowbirds (Molothrus ater) and intense predation on nests generally result in low reproductive success for Neotropical migrants regardless of forest size. In some midwestern U.S. landscapes, however, the variation in reproductive success among forest fragments suggests that `source' habitat could still exist for Neotropical migrants. We used vegetation, fragment and landscape metrics to develop multivariate models that attempt to explain the variation in abundance and reproductive success of Neotropical migrants nesting in an agricultural landscape in northern Indiana, USA. We produced models that reasonably described the pattern of species richness of Neotropical migrants and the abundance of wood thrushes (Hylocichla mustelina) and several other Neotropical migrant species within 14 forest fragments. In contrast, we were unable to produce useful models of the reproductive success of wood thrushes breeding in the same forest fragments. Our results suggest that (1) abundance patterns of Neotropical migrants are probably influenced by both landscape- and fragment-scale factors; (2) multivariate analyses of Neotropical migrant abundance are not useful in modeling the corresponding patterns of reproductive success; and (3) the location of any remaining `source' habitat for Neotropical migrants breeding within agricultural landscapes in North America will be difficult to predict with indirect measures such as vegetation composition or landscape context. As a result, the potential for developing conservation strategies for Neotropical migrants will be limited without labor-intensive, direct measurements of demographic parameters.