Long-term population trends in songbirds: Evidence from a general netting program

Abstract

A one-day-a-week general bird-netting operation has been conducted each autumn since 1965 at the UWM Field Station. Overall results for 23 years are presented, on a species by species basis. The 101 species captured were divided into three groups for a linear regression test for long-term population trends. Permanent residents showed no change over the 23 years. Short distance migrants exhibited a slight but not statistically significant decline. Long-distance migrants, on the other hand, exhibited a statistically significant decline, lending support to other studies which have reported population declines in North American songbirds that spend the winter in the tropics.