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AUTHORS: Nicole Keefner, Dr. Erik Blomberg - University of Maine
ABSTRACT: Ruffed grouse (Bonasa umbellus) occupy a wide distribution in North America, from Georgia in the south to Alaska in the north, as well as southern and central Canada. Color phases in ruffed grouse range from red, which is more prevalent at southern latitudes, to gray, which is more prevalent at northern latitudes. Some owl species exhibit similar latitudinal gradients in color phase, including tawny owls (Strix aluco) in the Old World and screech owls (Megascops asio) in the New World. These patterns are generally attributed to increased ability of gray morphs to survive northern winters. Although a number of mechanisms have been proposed for these relationships, recent studies on tawny owls have suggested that increased feather barb density in gray phase birds may provide an adaptive advantage in northern climates due to increased insulation. Our objective for this study was to evaluate if ruffed grouse exhibit a similar relationship between feather barb density and color phase. We collected dorsal and ventral body feathers from live-caught ruffed grouse and supplemented these with samples collected from harvested birds. We quantified feather length, plumulaceous length, and two barb density measurements for each feather using a dissecting microscope. We used generalized linear models to evaluate differences of feather barb density among color phases. Our results suggest gray phase and red phase individuals have similar feather barb density, inconsistent with the findings for tawny owls, and that insulating characteristics of feathers likely do not contribute to latitudinal gradients of color phase in ruffed grouse.
