Effects of prescribed burning on avian foraging ecology and arthropod abundance in sagebrush-grassland

Abstract

Effects of a prescribed burn on Brewer's sparrow (Spizella breweri) and sage sparrow (Amphispiza belli) foraging ecology were studied in a sagebrush-grassland of southeastern Idaho. Sparrows were observed during the nestling period from tower-blinds to document general feeding behavior, activity budgets, feeding rates, foraging patterns, and habitat selection before and after burning. After the fire, sage sparrows spent more time brooding and shading the nestlings and less time foraging, and males spent more time singing and defending their territories. Activity budgets of Brewer's sparrows did not change after the burn. Feeding rates (frequency and prey load size) of both species were unaffected by the fire. Brewer's sparrows flew farther from the nest to forage postburn, but feeding bout duration did not change. Sage sparrow feeding bout duration decreased after burning. Brewer's sparrows preferred to forage in areas with greater sagebrush (Artemisia spp.) coverage both preburn and postburn; male sage sparrows selected areas with greater grass and green rabbitbrush (Chrysothamnus viscidiflorus) coverage before but not after burning. I conclude that when prescribed burning results in a fine-grained mosaic with good interspersion of burned and unburned patches, both sage and Brewer's sparrows can continue to breed in burned areas, but fires that burn large patches would be detrimental to both species because of their feeding requirements.