Twenty-Year Recount of Bird Populations Along a Great Basin Elevational Gradient;Forest Service research paper

摘要

During 1981 and 1982, Dean E. Medin conducted bird censuses along an elevational gradient (5,250 to 11, 400 feet) near and on Wheeler Peak of east-central Nevada. Twenty years later we conducted bird census on seven of his 12 plots. Data from the bristlecone pine Pinus longaevaplot were collected in 1981 but not published (data on file with the Great Basin National Park). Data for the remaining six plots were collected in 1982 and published. In general, all 2002 bird counts from the seven study plots recorded substantially fewer numbers of total birds and, with the exception of the bristlecone pine and alpine study plots, recorded fewer bird species as compared to Medins counts of 1981 and 1982. Total numbers of birds counted in the 70 visits (10 census visits for seven study plots) to all study plots for 1981 and 1982 was 5,034. This compares to 1,930 for 2002, or a reduction of 3,104 birds - a 62 percent reduction. Total number of bird species sighted in 1981 and 1982 was 83 compared to 75 in 2002, or a reduction of eight. Sixty-three species of birds were common to the 1981/1982, and the 2002 censuses. Twenty species of birds were sighted in 1981 and 1982 that were not sighted in 2002, and 12 species were sighted in 2002 that were not recorded in 1981 and 1982.