Geographic Variation of Group Size, Ontogeny, Rattle Calls, and Body Size in Aphelocoma ultramarina

Abstract
We estimated sizes of over 90 social groups of Aphelocoma ultramarina in various regions of Mexico and recorded the presence or absence of Rattle calls. Group size over most of Mexico was simiilar to that in Arizona, not to that in Texas, [USA]. We found that geographic variation in mean group size was not correlated with ontogeny of bill color. Group size correlated positely with body size. Rattles were found only in A. u. couchii but not in all populations. We hypothesize that natural selection may not be the only factor responsible for the patterns observed.