Do conversational gutturals help florida scrub-jays coordinate their sentinel behavior?

Florida scrub-jays, Aphelocoma coerulescens, perform sentinel behavior in which individuals alternate bouts of watchfulness with little overlap. We examined how calls might facilitate sentinel coordination. Small soft calls labeled conversational gutturals were heard more often from sentinels than from foraging birds. Calls occurred infrequently throughout sentinel bouts but were more common later in bouts. The pattern of calling does not match predictions for a 'watchman's song' at regular intervals nor for a signal at the end of a sentinel bout. Thus, our quantitative assessment of calling by sentinels did not find support for either standard hypothesis. Although Florida scrub-jays clearly have information on each other's sentinel behavior, our results suggest that calls provide perhaps a fraction of this information.