14 years 10 months ago
A 15 and 20-Year Summary of Breeding Bird Trends in National Forests of Northern Minnesota and Wisconsin
Niemi, Gerald J; Howe, Robert; Danz, Nicholas P; Etterson, Matthew
The breeding bird communities of the western Great Lakes region have among the richest diversity of breeding bird species in North America (Robbins et al. 1987; Green 1995, Rich et al. 2004). The importance of this diversity and concerns with potential declines of some species has led to a strong interest in monitoring forest bird populations in the region. The relatively heavily forested landscapes of northern Minnesota and Wisconsin are considered to be population 'sources' for many forest bird species and may be supplementing population 'sinks' in the agricultural landscapes of the lower Midwest (Robinson et al. 1995, Temple and Flaspohler 1998). Analysis of population trends is used as an 'early-warning system' of potential problems in a species population and serves as a measure of the ecological condition of the environment (Niemi and McDonald 2004).
Large-scale population monitoring programs such as the U.S. Geological Survey’s Breeding Bird Survey (BBS) provide important information on trends at a continental scale. However, limited coverage in some areas can make it difficult to use BBS data to characterize population trends at smaller geographic scales (Peterjohn et al. 1995). Continental trends also have the potential to mask regional population trends (Holmes and Sherry 1988), thus there is a need for regional monitoring programs that can provide more localized information (Howe et al. 1997). In response to the need for regional population data, a long-term forest breeding bird monitoring program was established in 1991 in the Chippewa and Superior NFs, and in 1992 in the Chequamegon NF. The Forest Service is mandated to monitor certain management indicator species (Manley 1993), and our monitoring program expands beyond indicator species to include all forest songbird species that we can adequately sample. Currently, approximately 420 stands (1,271 points) within the three national forests are surveyed during the breeding season (June 1 to July 10).
The primary objective of this report is to update U.S. Forest Service personnel on results of the forest bird monitoring program. Here we focus on relative abundance trends of individual species. Because we slightly changed our point count methodology in 1995 by including unlimited point counts, here we focus on a comparison of the results from three different distance radii x time categories: 1) 100 m radius distance for 1991-2009, 2) 100 m radius distance for 1995-2009, and 3) unlimited distance for 1995-2009. Our intent here is to summarize the most important results and to provide detailed information in appendix form for those who need more specific results.