Role of Helpers in the Sentinel Behaviour of the Florida Scrub Jay (Aphelocoma c. coerulescens)

Abstract

AbstractTwo independently conceived and executed field studies using somewhat different methodologies tested the hypothesis that non‐breeding helpers of the Florida scrub jay (Aphelocoma c. coerulescens) contribute importantly to antipredator sentinel behaviour. Specifically, we made four predictions: 1. Helpers participate to a non‐trivial degree in sentinel behaviour; 2. Breeding pairs with helpers spend less time on sentinel behaviour and hence more time foraging; 3. Breeders with helpers have more protected foraging time; and 4. Groups with helpers have greater total sentinel time.Results of the two studies agreed on most major points and even, in many cases, on minor points and quantitative aspects. Non‐breeding adult helper birds participated in sentinel watches almost as much as breeders in their group. In winter, breeding pairs with one or more helpers decreased their own sentinel time compared with that of unassisted pairs. However, in the one study, the concomitantly increased available foraging time of breeders was no better protected by another group member being on sentinel than in the lone pairs. Results of the other study showed a significant increase of protected foraging time for breeding males only. In winter, groups with helpers did not have increased total sentinel time; time was either the same (Study A) or significantly less (Study B). During nesting, breeders with helpers did not decrease their sentinel effort relative to lone pairs. Instead, groups with helpers had a sentinel for more time. These results are interpreted as indicating that, in winter, sentinel behaviour is more important to antiraptor defense in lone pairs than larger groups. In groups with helpers the mere addition of extra pairs of eyes and ears may render formal sentinel behaviour less necessary, so breeders can decrease their sentinel time and increase their foraging time. During nesting, additional sentinels may be important for increased nest protection. The presence of helpers contributing to predator detection may thus be an important factor in the better annual survival and nesting success of breeders that have helpers (Woolfenden & Fitzpatrick 1984).