Avian Population Trends in the Pacific Northwest

Land bird populations are facing a growing number of threats including habitat loss, climate change, loss of stratospheric ozone, and toxic pollution. In response to land bird monitoring needs by federal agencies, the High Cascades Ranger District in Prospect, OR, began implementation of mist-netting efforts as established by the Monitoring Avian Productivity and Survivorship (MAPS) program in 1994. Site specific population trends were analyzed using regression and non metric multi-dimensional scaling (NMS) ordination analysis over a fourteen year period, and then compared to regional trends using the MAPS web-based query. Of thirty nine species, four demonstrated significantly increasing trends, while two species demonstrated significantly decreasing trends in regression analysis. Site-specific trends were consistent with regional trends. Regression analysis also revealed a significant correlation between abundance and climate factors, specifically temperature and precipitation. The NMS ordination did not reveal clear ecological trends, but did show that species composition varies with net placement. Climate factors, life history strategy, productivity, and survivorship were factors used to interpret population trends. Continued MAPS monitoring will facilitate our understanding of shifts in avian populations and their ranges that will most likely occur in light of increased land use and climate change.