A sentinel system in the Florida scrub jay

Abstract One postulated advantage of living in groups is increased protection from predators. Living in small, permanent groups of stable composition allows for the formation of a sentinel system, in which individuals coordinate their vigilance. Florida scrub jays, Aphelocoma coerulescens coerulescens , live in family groups, and coordinate their vigilance into a sentinel system. Observed vigilance behaviour was compared with models generating similar behaviour patterns at random. The occurrence of one jay terminating vigilance in the same minute that another initiated vigilance was greater than expected by chance, and the occurrence of more than one vigilant jay at one time was less frequent than expected by chance. The seasonal pattern of scrub jay sentinel behaviour suggests that it functions primarily for predator detection, especially of raptors. Most aerial predator alarm calls were given by sentinels, and a sentinel was most likely to give the alarm call first.

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