Foraging, home range use and social behaviour of a group‐living rainforest raptor, the Red‐throated Caracara Daptrius americanus

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A stable group of six Red‐throated Caracaras Daptrius americanus was followed over 5 years in a rainforest area of French Guiana and was intensively studied during 52 days in 1989‐90. They bred successfully only twice (1986 and 1990). Communal nest guarding and brood care were observed. Their social behaviour and group‐living habits seem unique among raptors. The 400‐ha all‐purpose, year‐round, group territory was defended by all individuals and was almost fully used. The birds foraged individually, but the cohesion of the group and its coordinated movements were maintained by periodic loud rallying calls. Food sharing of large prey items and even deliberate allofeeding also contributed to the group cohesion. Mature, high, closed‐canopy forest was preferred and 88% of the actively foraging birds were encountered in the understorey, where they had a higher success rate than those hunting in the upper canopy. This may explain why the species' frequency and group size markedly decreased in secondary or disturbed forests. The 12‐hour daily activity period was reduced by an average of 2 hours either by a midday pause (hot weather) or by rains. At least 74% of all food items taken were wasp nests or other insect nests in the foliage, 9% were hard fruits, and the remaining captures were various invertebrates or unidentified items. When the caracaras were raiding a wasp nest, the wasps were kept off probably by a powerful repellent, a striking adaptation unprecedented among birds. Several species of mostly large canopy frugivores regularly formed close associations with the caracaras to forage in the understorey, where they otherwise rarely or never ventured. This new interspecific flocking behaviour is interpreted as an antipredator strategy benefiting from the raptors' warning and mobbing efficiency.