Aphelocoma ultramarina Nov. 6-10 Casita, 40 km. S Nogales, 3300 feet, Sonora. Observed daily in flocks of usually 10 to 25 birds; rarely seen in small numbers or as lone individuals, these apparently being temporarily stragglers from flocks to which they belong and probably not far distant. Four to six flocks were encountered in the course of a full morning's cruising. Behavior of flocks which were followed for periods of 1/2 to 1 hour as well as flocks met two or three times at a given location suggest that they are actually more local in their wandering than would at first appear to be the case. Flocks were made up of adults and first-year birds. The chief note of this species is a unjay-like, nasal and harsh, upsprung with or week strongly suggesting (a) commonote of the house finch, but much amplified. This note was given repeatedly by the individuals of a flock in flight; also when part of the flock was in flight, or when the birds were in any way disturbed or alarmed. It clearly served as an alarm note and flocking note. While foraging, members of a flock uttered only a soft trink, apparently merely a conversational note, similar to that of A. coerulescens.