Vocal production, auditory perception, and signal active space in an open habitat specialist, the Grasshopper Sparrow

Abstract

Grasshopper Sparrows are specialists in open grassland habitats and face acoustic challenges normally associated with that habitat type. They produce several types of calls and two distinct types of song, all of which are high-pitched for songbirds (6—10 kHz). The primary territorial song, also known as the “buzz” song, consists of 3 or 4 brief introductory notes followed by a high-pitched, rapidly modulated trill. The function of the secondary song type, or “warble” song, remains unknown, but data from autonomous recording units demonstrates a correlation with pairing status and breeding cycle timing. Operant discrimination tests with Grasshopper Sparrows show a broader audiogram and extended high frequency auditory limit when compared with other small songbirds, suggesting that these birds, and potentially related species as well, have evolved a wider spectral range of auditory sensitivity in this habitat type. Auditory detection and discrimination thresholds were used to explore the active space and co...