Modeling ruffed grouse populations in the central and southern Appalachians

John Michael Tirpak, Fordham University

Abstract

From 1995–2002, the Appalachian Cooperative Grouse Research Project conducted a radiotelemetry study of ruffed grouse ( Bonasa umbellus) on 7 study areas in 5 states—Pennsylvania, Maryland, West Virginia, Virginia, and North Carolina. Based on this data, grouse populations were declining on all sites. However, declines were steeper than trends based on either Breeding Bird Survey or Christmas Bird Count data. When survival and/or reproductive windows, which increased vital rates to their empirical maxima, were included in models to mimic mast years, population growth more closely resembled regional trends. The finite rate of increase was most sensitive to brood survival, and most elastic to non-breeding survival of adults. Because grouse populations appear to be affected by forest composition at the landscape scale, I used multitemporal Landsat imagery to differentiate evergreen, hardwood, and oak overstories, as well as evergreen and non-evergreen understories, on these study areas. Additionally, I developed standardized datasets for topographic moisture index, stand age, and roads—other landscape features that potentially affect ruffed grouse. To determine habitat preferences, I compared these habitat features within grouse home ranges and equally-sized buffered random points. Grouse were positively associated with roads and <20 year old>forest, but sex and age affected habitat preferences. Males used younger forest than females, due to differential habitat use during spring. Juveniles had less of the habitats preferred by adult grouse within their home ranges, indicative of competitive exclusion. Models of adult female home ranges contained the most parameters, reflecting greater specificity and selectivity of females to habitat conditions. I also determined the influence of habitat composition on longevity, nest success, and daily brood survival. Longevity of adult females reflected winter habitat requirements, while adult males were most strongly associated with early successional forest. Nest success was associated with older forest, emphasizing the need for interspersion of habitats. Brood survival responded strongest to topography, and was highest in mesic areas. Combining models of habitat preference with longevity and reproduction allowed identification of sources and sinks. Across areas, the majority of suitable habitat served as sinks. However, these sinks may become source during high mast years. ^

Subject Area

Biology, Ecology|Agriculture, Forestry and Wildlife

Recommended Citation

John Michael Tirpak, "Modeling ruffed grouse populations in the central and southern Appalachians" (January 1, 2005). ETD Collection for Fordham University. Paper AAI3182454.
http://fordham.bepress.com/dissertations/AAI3182454

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