Abstract
Abstract In an Arizona study the population of cavity-nesting birds declined by 52 percent on a plot in ponderosa pine (Pinus ponderosa Laws.) when conifer snags were removed during a timber harvest but some quaking aspen (Populus tremuloides Michx.) snags were left standing. On an adjacent plot where snags were left standing, birds increased by 23 percent. There was also a 31-percent increase on an unharvested control plot. Population of violet-green swallows (Tachycineta thalassina) decreased from 20.7 pairs per 100 acres to 2.2 pairs on the plot where snags were removed. There was no significant change in populations of open-nesting birds but gray-headed juncos (Junco caniceps) and American robins (Turdus migratorius) increased on all plots.
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