Response of passerine birds to forest edge in coast redwood forest fragments

The response of passerine birds to forest edge was examined in old-growth a nd mature second-growth coast redwood (Sequoia sempivirens) forest in north ern California. The study objectives were to determine which common passeri ne species are sensitive to edges during the breeding season and to estimat e edge width for forest interior species. Response to edge was measured alo ng twelve 100 X 400 in plots extending from the edge into the forest interi or to obtain relative density of birds. Plots were surveyed 4 to 5 times in 1996 and 8 to 10 times in 1997. We found that 14 common passerines showed a gradient of edge sensitivity. Steller's Jay (Cyanocitta stelleri) and Swa inson's Thrush (Catharus ustulatus) had higher relative densities near edge s than in the forest interior (P < 0.05) and were categorized as edge speci es. Brown Creeper (Certhia americana), Winter Wren (Troglodytes troglodytes ), Pacific-slope Flycatcher (Enipialonax difficilis), and Varied Thrush (Ix orcus naevius) had lower relative densities near edges (P < 0.05) and were categorized as interior birds. Based on exponential regression models, esti mated edge widths were 140 in for Varied Thrushes, 85 in for Brown Creepers , 120 in for Winter Wrens, and 125 in for Pacific-slope Flycatchers. Creati on of edges would probably benefit Steller's Jays (which may be a nest pred ator), may not benefit Swainson's Thrushes, and may be detrimental to speci es that avoid edges. We recommend that edge effects be taken into considera tion when planning for the conservation of bird species in the region.