PARENT SESSION
Oral Session 2: Avian Ecology I: Habitat and Disturbance.
Presiding: D Miles and C Lepczyk
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room A 106.
Influence of alternative silvicultural practices on songbirds in western Oregon.
Hayes, John1, Stoddard, Margo*,1, Chambers, Carol2, 1 Oregon State University, Corvallis, OR2 Northern Arizona University, Flagstaff, AZ
ABSTRACT- Uneven-aged forest management practices have been proposed as alternatives to clearcutting in part because the structural complexity that results may benefit vertebrate groups such as songbirds. However, few studies have examined the validity of this hypothesis. We determined the relative influences of three alternative silvicultural practices on abundance and diversity of songbird populations, and examined changes in relative measures of species abundance over time by comparing results of data collected immediately after harvest (1990-1992) with data collected in 2002 and 2003. The study sites consist of sets of control stands and three silvicultural treatments (clearcut, two-story stands, and patch cuts) replicated in three blocks in Oregon State University's MacDonald-Dunn Forest. We conducted 6 point counts at 2-3 stations in each stand between mid-May and early July 2002-2003. A total of 11041 bird detections representing 72 species were noted within all variable circular plots in all treatments. Percentages of detections were comparable in the modified clearcut (32%), two-story (32%), and patch cuts (28%). Among species detected >30 times (n=42), 25 showed patterns suggesting differences in mean number of detections per visit could be attributed to differences in open (modified clearcut and two-story) vs. closed (control and patch cut) habitat. These trends are consistent with results from analyses of the bird community composition among treatments immediately after harvest. However, relative number of detections over time differed for several species. For example, in open stands, Swainson's thrushes increased whereas white-crowned sparrows decreased. These results emphasize the importance of conducting long-term studies to fully understand of the influences of alternative silvicultural approaches on songbirds.
Key words: forest management, bird communities, uneven-aged management