Avian Community Changes in Relationto Different Forest Fire Conditions in Central Idaho

Abstract

Wildfire is an important driver of forest bird communities in western North America. To fully understand wildfire effects, more studies comparing species-specific responses across space, time, and a range of burn severities are needed. We analyzed point count data (n = 809 point × year survey occasions; 2002–2010) from central Idaho to examine forest bird community responses to fire. Using community occupancy models, we analyzed changes in point occupancy before and after prescribed burning and wildfire, and along a post-wildfire burn-severity gradient. Occupancy patterns were largely consistent with those expected from species life histories. Cavity nesters and aerial insectivores (mountain bluebird [Sialia currucoides; n = 37 survey occasions detected], house wren [Troglodytes aedon; n = 15], Olive-sided Flycatcher [Contopus cooperi; n = 15]) responded positively to fire consistent with increases in nesting substrate and foraging opportunities expected for these species. Shrub-nesting species (lazuli bunting [Passerina amoena; n = 75], Black-headed Grosbeak [Pheucticus melanocephalus; n = 29]) exhibited lagged positive responses with the expected lag in shrub development after wildfire. In contrast, canopy-nesting foliage gleaners and pine-seed consumers (Clark’s nutcracker [Nucifraga Columbiana; n = 50], Townsend’s warbler
[Setophaga townsendi; n = 133]) responded negatively to wildfire. More species responded positively than negatively to fire, and responses to high-severity wildfire were stronger than to prescribed burning. Consequently, species richness increased by approximately 3 species from low- to high-severity burned points and pre- to post-wildfire years. Our results suggest high-severity wildfires generate important habitat for many species, contributing positively to avian diversity.