Identification of Individual and Population-level Variation in Vocalizations of the Endangered Southwestern Willow Flycatcher (Empidonax traillii extimus)

Abstract

Abstract.— An understanding of individuality in animal vocalizations can assist in tracking individuals spatially and temporally, and is particularly useful for species of conservation concern. We determined whether fitz bew vocalizations of the endangered Southwestern Willow Flycatcher (Empidonax traillii extimus) showed vocal individuality, assessed the differences in vocal individuality among three populations, and tested the ability of predictive vocalization models to reidentify individuals. Fitz bew vocalizations were recorded from two populations in Arizona (Roosevelt Lake and San Pedro River) and one in California (Kern River). Individuality was determined using discriminant function analysis (DFA) and trained artificial neural networks (ANN). Southwestern Willow Flycatchers showed individuality in the fitz bew, with the models correctly classifying 81–86% of the vocalizations. We also found population-level variations: vocal structure differed substantially between Roosevelt Lake and Kern River, ...