A Forty-year Comparison of the Breeding Avifauna in Grand Teton National Park, Wyoming

摘要

Studies comparing historical data with modern surveys can provide important insights into avian population trends. In 1993-1995 I repeated a breeding bird survey completed by G. W. Salt in 1952 and 1954 in Grand Teton National Park, Wyoming. The composition of breeding birds on all transects were comparable during the four decades, with most species showing no discernable difference in relative abundance (60.7%; n = 54), although 45.6% (n = 41) showed strong annual variation in the 1990s. Long-distance migrants represented the greatest number of species present (52.8%; n = 47) and the largest proportion showing a decline (25.5%; n = 12). Resident species had the largest proportion showing an increase (31.8%; n = 7). One resident species (Clark's nutcracker, Nucifraga columbiana) and one short distance migrant (red-naped sapsucker, Sphyrapicus nuchalis) showed a declining trend. American bitterns (Botaurus lentiginosus) may have disappeared from the sites surveyed in this study. Willow flycatcher (Empidonax traillii) abundance, while highly variable in the 1990s, also showed a significant decline. Close to half of the species occurring in spruce-fir forest declined (42.2%; n = 11), while species occurring in lodgepole pine (Pinus contorta) forest increased (35.3%; n = 12). Large national parks, such as Grand Teton National Park, could act as avian refugium, fundamental in preserving species that are experiencing declines in surrounding areas or on wintering grounds. The value of relatively undisturbed landscapes, such as national parks, to protect and conserve species numbers and diversity is increasingly vital, as the landscape and habitat in the surrounding areas continue to change. [PUBLICATION ABSTRACT]