FIRE AND HABITAT EXPLAIN GEOGRAPHIC VARIATION IN TYPE I SONGS OF HERMIT WARBLERS IN CALIFORNIA, USA.
Brett J. Furnas; California Department of Fish and Wildlife; 1701 Nimbus Road, Suite D, Rancho Cordova, CA, 95760; (530) 227-3998; brett.furnas@wildlife.ca.gov; Russ H. Landers, Rauri C. K. Bowie
As an epiphenomenon, geographic variation in song dialects may help us better understand the functional diversity of traits within an avian species. Hermit warblers (Setophaga occidentalis) sing a highly-stylized, type I song to attract mates, in contrast with a repertoire of more complex, type II songs to defend their territories. There is often a single, dominant type I song, or a low diversity of type I songs, within the same geographic area. This study provides the first comprehensive description and mapping of Hermit Warbler type I song dialects throughout California, USA. During the period 2009 to 2014, we recorded type I songs from 1,576 males from 101 study areas across the state from April to July. We used those locations and a pre-existing range map for the species to create a maximum entropy-based breeding habitat suitability map for the entire state. We classified the songs into dialects consisting of 35 local forms within 14 regional super-forms. We modeled the effects of distance between territories, habitat quality, and recent fire history (10 years) at the local (315 km2) and regional (8,000 km2) scales to explain whether birds sang the same dialect as each other. We found that the probability of singing the same dialect declined with distance between breeding territories. The probability of sameness increased with local habitat quality but decreased with regional habitat quality; song sameness declined with the amount of local fire but increased with the amount of regional fire. These findings demonstrate how multi-scale patterns in habitat availability and fire history explain the diversity of song dialects. Taken together, they suggest that fire at the local scale and mass effects of rival dialects at the regional scale disrupt the uniformity of song dialects within a locale.
Poster Session