COMPARISON OF BIRD COMMUNITIES IN SOUTHWESTERN MONTANA AFTER FOURTEEN YEARS OF NATURAL RECOVERY FROM SMELTER IMPACTS

摘要

Fourteen years after closure of the Anaconda smelters in southwestern Montana, birds were surveyed during the 1994 breeding season along stratified random transects on three areas close to the smelters. Vegetation on these proximal sites had been altered by emissions during the 96 years of smelter operation. Comparable surveys were performed on a more distant reference area. Numbers of species and numbers of birds on the affected sites did not differ significantly from those on the reference area. One of the affected areas had significantly more species than the reference site for the main affects model (ANOVA, p=0.010) and for conifer habitat (ANOVA, p=0.014). Species richness expressed in rarefaction curves was comparable among areas, but species similarity differed. Smelter effects on the vegetation and subsequent natural recovery, since closure of the smelter in 1980, have created a mosaic of vegetation communities on the affected sites and increased the horizontal diversity of bird habitats (Mann-Whitney Test). These changes appear to have produced the high species richness and abundance of birds found on the affected sites.