The Effect Of Forest Fragmentation On Birds In Spruce-Fir Old-Growth Forests

Authors(s): M. E. Keller

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Publication Date: 0000-00-00

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Location: Laramie WY

Abstract: A three year study investigated the avifauna of subalpine old-growth forests and the effect of forest fragmentation on these birds. In 1984, the avian community of old-growth spruce-fir forests at mid and high elevations was compared. The golden-crowned kinglet and Swainson's thrush were both common at mid-elevations but rare or absent at higher elevations. Avifauna of younger seral lodgepole pine stands was also described. In 1985 and 1986, avian relative abundance was measured in four sets of paired fragmented and unfragmented stands to assess the effect of forest fragmentation on avian abundance. Fragmented stands were interspersed with strip cuts or spotcuts. The brown creeper and red-breasted nuthatch were considered to have the strongest negative response to fragmentation; they had lower abundance in fragmented stands and were associated with plots surrounded by old-growth and containing a higher density of large live trees and snags. It was suggested that fragmentation lowers the density of large trees used for foraging, below acceptable levels. Pine siskins and Cassin's finches had the strongest positive response to fragmentation, having higher abundance in stripcut stands and being associated with plots containing clearcuts. The gray jay, mountain chickadee, and ruby-crowned kinklet had little response to fragmentation. The distribution of species in relation to forest edges was not a strong predictor of species sensitive to fragmentation. Snags used by foraging three-toed woodpeckers were characterized and described. Analysis of these foraging sites indicated that three-toed woodpeckers were selecting larger diameter snags than were generally available and predominantly foraged on the southeast face of the snags where morning surface temperatures would be warmest. The highest density of used snags was in the stand containing the highest density of available snags. All aspects of these foraging sites suggested highly selective and efficient use available resources and concur with the literature that this species of woodpecker may be an important factor in the control of forest insects.

Keywords: animal , Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, bird, Aves, ornithology, golden-crowned kinglet, Regulus satrapa, Swainson's thrush, Catharus ustulatus, habitat, population, pine siskin, Carduelis pinus, Cassin's finch, Carpodacus cassinii, jay, Corvidae, gray jay, Perisoreus canadensis, mountain chickadee, Parus gambeli, ruby-crowned kinglet, Regulus calendula, three-toed woodpecker, Picoides tridactylus, insect, Insecta, entomology, food