Variation of Western Scrub-Jay and Mexican Jay (Corvidae) vocalizations in Texas

Abstract

I recorded vocalizations of allopatric populations of Western Scrub-Jays (Aphelocoma californica texana and A. c. woodhouseii) and Mexican Jays (A. ultramarine couchii) at eight sites in Texas. While many call types were inconsistent in structure and tended to intergrade, I identified two structurally distinct call types (the flight call and the rattle call) as shared by all taxa at all sites. Differences in acoustic structure of both call types were greatest between species. Subspecies showed less distinct acoustic structure, with unique acoustic structures occasionally being shared with the nearest population of another subspecies. Morphometric acoustic analysis revealed a similar pattern, with the most differentiation at the specific level, followed by subspecific and, lastly, by populational differentiation. Of particular interest was a small, isolated population of A. californica found in the Texas panhandle. Although breeding populations may have existed for only two or three decades, morphometric analysis of both call types showed marked vocal differentiation from other Texas Scrub-Jays. Analysis of one call type suggested morphometric acoustic separation from the other populations of Scrub-Jays at the subspecific level, while the other call type suggested separation at the specific level.