Spring and Winter Bird Populations in a Douglas-Fir Forest Sere

Abstract

Changes in bird species richness, abundance, and guild structure were compared among young (42-75), mature (105-165), and oldgrowth (250-500+ years) and between winter and spring, for 2 years in Douglas-fir (Pseudotsuga menziesii) forests of the southern Washington Cascade Mountains. In winter, bird species richness, diversity, and abundance were all greater in oldgrowth than in younger stands. The most abundant species were the chestnut-backed chickadee (Parus rufescens), golden-crowned kinglet (Regulus satrapa), pine siskin (Carduelis pinus), and red crossbill (Loxia curvirostra). In spring, there were few differences in diversity and abundance along the stand age gradient. Species richness showed a slight increase from young to oldgrowth. The most abundant spring species were the winter wren (Troglodytes troglodytes), western flycatcher (Empidonax difficilis), varied thrush (Ixoreus naevius), hermit warbler (Dendroica occidentalis), and chestnut-backed chickadee. The Vaux's swift (Chaetura vauxi) exhibited the strongest association with oldgrowth in the spring. Seasonal changes in abundance were greater in young and mature stands than in oldgrowth. This pattern was most noticeable among permanent resident species. A more favorable microclimate and probably better foraging conditions in oldgrowth in winter may explain the observed seasonal patterns of abundance. J. WILDL. MANAGE. 51(3):586-595 Even though the importance of the breeding season has been strongly emphasized as shaping bird communities, the winter season may be equally critical (Fretwell 1972), especially in regions where large numbers of species occupy the habitat throughout the year. Seasonal population changes, particularly of permanent residents, may provide an indirect measure of habitat quality. Forests of different age may provide different levels of resources, and therefore, may vary in quality. The published accounts by Raphael (1984) and Raphael and Barrett (1984) provided comparable studies for late successional Douglas-fir forests in northern California. The purpose of our study was to document the seasonal changes in bird community structure within a sere of natural Douglas-fir forests and o speculate on the effects of forest management on bird communities during both the winter and breeding seasons. We express our appreciation to M. Q. Affolter, B. Booth, J. B. Buchanan, C. B. Chappell, M. This content downloaded from 157.55.39.123 on Tue, 18 Oct 2016 06:04:41 UTC All use subject to http://about.jstor.org/terms J. Wildl. Manage. 51(3):1987 BIRDS IN DOUGLAS-FIR * Manuwal and Huff 587 Emers, K. W. Hegstad, A. Hetherington, A. B. Humphrey, D. A. Leversee, R. W. Lundquist, J. M. Mariani, B. R. North, M. J. Reed, B. A. Schrader, and L. A. Willimont for assistance with the fieldwork. N. J. Manuwal, J. G. Dickson, R. W. Mannan, R. W. Lundquist, and J. B. Buchanan provided valuable comments on the manuscript. We thank J. M. Mariani for many long hours of data editing and calculation of detection rates for the winter 1984-85 data, and J. R. Osborne for his computer expertise. We thank U.S. For. Serv. personnel at the Wind River, St. Helens, Randle, and Packwood ranger districts and Mt. Rainier Natl. Park personnel for various assistance. We acknowledge the support of L. F. Ruggiero, A. B. Carey, and F. B. Samson. This study was funded by contracts PNW-83-219 and PNW-84-227 and is Contrib. 44 of the Old-growth Wild. Habitat Res. Pro-