Abstract:
Vocalizations of scrub jays (Aphelocoma coerulescens texana and A.c. woodhouseii) and gray-breasted jays (A. ultramarina couchii) were recorded at eight sites in Texas. All three taxa were considered allopatric. While many call types were not consistent in structure and tended to intergrade, two structurally distinct call types were identified as shared by all taxa at all sites. Differences in acoustic structure of both call types was greatest between species. Acoustic structure between subspecies was less distinct, with unique acoustic structures occasionally being shared with the nearest population of another subspecies. Morphometric 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. coerulescens 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 separation from the other populations of scrub jays at the subspecific level, while the other call type suggested separation at the specific level.