EFFECTS OF THE ROOST SITE ON THE ENERGETICS OF BLACKBIRDS AND STARLINGS

To augment their physiological and physical thermoregulatory capacity, many birds display long-term behavioral adjustments; the significance of this has been considered, yet detailed information is lacking (Dawson and Hudson 1970; Calder and King 1974). One such behavioral adjustment appears to be communal roosting in sheltered areas during winter nights. This behavior has been demonstrated in nuthatches (Sitta spp.) (Knorr 1957), finches (Leucosticte spp.) (French 1959; King and Wales 1964), eastern bluebirds (Siala sialis) (Frazier and Nolan 1959), red-winged blackbirds (Agelaius phoniceus), brown headed cowbirds (Molothrus ater), bronzed grackles (Quiscalus quiscula) (Francis 1976), and starlings (Sturnus vulgaris) (Francis 1976; Yom-Tov et al. 1977). Congregating in sheltered roost sites must alter some of those environmental factors which comprise the thermal climate space (Porter and Gates 1969) of the organism, and in doing so, confer an energetic advantage upon the inhabitants. To further quantify the energetic advantage of the starling\u27s nocturnal roost site selection in a dense coniferous pine woods, this study was undertaken to determine: (1) what microclimate factors distinguish areas of the pine woods selected as nocturnal roost sites from those that are not, and (2) what is the energetic advantage of roost site selection, and is this advantage dependent upon large roosting concentrations of birds