Population ecology of grassland sparrows on reclaimed surface mine grasslands in Pennsylvania

Grassland sparrow populations have experienced substantial declines across their range, and reclaimed surface mine grasslands have been recognized for their importance to grassland sparrow populations. To understand how woody vegetation and landscape components affect grassland sparrow ecology on reclaimed surface mine grasslands I implement two research projects.;For the firstresearch project, I monitored grasshopper (Ammodramus savannarum) and Henslow's (A. henslowii) sparrow population dynamics over a three-year period (2009--2011) across eight 20.2 ha plots of surface mine grasslands with various amounts of scattered woody vegetation coverage (~5--36%) in Pennsylvania. Using a before-after-control-design for pairs (BACIP), woody vegetation was removed from treatment plots following the first breeding season. I monitored daily nest survival (DNS), interspecific brood parasitism rates, fledgling production and calculated changes in apparent survivorship, juvenile return rates, and population growth rates in response to woody vegetation removal. Following woody vegetation removal the DNS of 216 nests was unaffected by either the density of woody vegetation around a nest, distance to closest shrub, or shrub coverage percent for either species. I recorded no incidences of interspecific brood parasitism by brown cowbirds (Molothrus ater). Fledgling production from successful nests, however, declined slightly as woody vegetation coverage increased across plots. My results suggest that the presence of woody vegetation on reclaimed surface mines does not necessarily equate to poor nesting habitat for grasshopper and Henslow's sparrows, and that both species successfully nest and produce young in habitats with greater amounts of woody vegetation than has previously been considered. The grasshopper sparrow apparent survival rate did not differ between control and treatment plots. Henslow's sparrow populations, however, experienced a three-fold decrease in apparent survivorship following woody vegetation removal compared to Henslow's sparrow populations on control plots. The overall grasshopper sparrow population size across treatment plots increased by 14% from 2009--2011 while the overall population on control plots declined. Henslow's sparrow populations declined more rapidly on treatment plots compared to control plots over the same time period. Henslow's sparrow population size for any given plot and year was 0.12 the size of the grasshopper population on that plot. I observed low juvenile annual return rates for Henslow's and grasshopper sparrows across all plots. My results suggest that removal of woody vegetation from surface mine grasslands has a positive and immediate effect on grasshopper sparrow populations and no positive effect on Henslow's sparrow populations at least during the two years following woody vegetation removal.;In the second research project I used unpublished data from 2002and newly-collected data from 2011 to estimate how grasshopper and Henslow's sparrow densities and surface mine vegetation have changed during those 9 years. I visited 61 surface mine grasslands in 2011; twenty-three of those had been previously visited in 2002. Vegetation changed very little over those 9 years, but woody vegetation increased by 2.6 fold, and grasshopper and Henslow's sparrows declined by approximately 13% and 7% per year, respectively. Grasshopper sparrows were 2.41 times more likely to occupy a grassland than Henslow's sparrows, and both species were more likely to occupy large and simply-shaped grasslands with low perimeter-to-area ratios and with few woody shrubs that were dominated by grass cover. My results suggest that without management that reclaimed surface mine grasslands are ephemeral habitats, but that low densities of both species occur on small grasslands (≤13 ha) and on grasslands with extensive woody vegetation coverage (up to one woody shrub per 16.5 m 2). Forecasted declines in Appalachian coal production over the next several decades will likely result in a 50% reduction of newly-created reclaimed surface mine grassland. Populations of grasshopper and Henslow's sparrows in Pennsylvania will likely continue to decline as they become concentrated on these small, isolated and woody grasslands. (Abstract shortened by UMI.).