Influence of Prescribed Fire on Winter Abundance of Bachman's Sparrow

Abstract

Prescribed fire is used extensively to manage breeding habitat for Bachman's Sparrow (Aimophila aestivalis), but little is known about the effects of prescribed fire on winter habitat requirements. We used conspecific recordings in conjunction with point counts to assess relationships between winter sparrow abundance and use of prescribed fire. Counts of sparrows conducted over three winters were higher (0.59 ± 0.42) (x̄ ± SD) when surrounding vegetation was burned the previous breeding season than in areas burned >18 months earlier (0.27 ± 0.38). Year-to-year abundance estimates for individual stations increased an average of 0.39 (± 0.54) individuals per count when surrounding vegetation was burned the previous breeding season and decreased 0.22 (± 0.59) individuals per count when vegetation was not burned. Sparrow counts were positively correlated with percent bare ground cover surrounding census stations and negatively correlated with increases in percent grass cover, grass standing crop, height of grass, and shrubs <1 m in height. Prescribed fire may improve winter foraging conditions for this ground-dwelling species by reducing dense grass cover at ground level. Increased flowering responses that many dominant plants exhibit following burns also may improve winter food resources. We observed color-marked birds (n = 18) in the same areas used during the breeding season and confirmed the maintenance of year-round home ranges by some individuals.