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Sparrowhawks feed with treeshrews and drongos, rather than on them

In general, mixed-species foraging associations may form to enhance feeding success or to avoid predators. Mixed foraging flocks of birds have been studied in different parts of the world. Though birds of prey have been observed to participate in foraging associations, these have typically been with taxa that are larger and not at risk of predation, such as the association between double toothed kites and capuchin monkeys. In this study, we reported a unique foraging association between the Nicobar treeshrew (Tupaia nicobarica), a little known, small mammal, and two species of birds, the greater racket-tailed drongo, (Dicrurus paradiseus) and a sparrowhawk, which is a potential predator (Genus Accipiter). The sparrowhawk, instead of attempting to prey on the treeshrew and drongo, participates in the mixed flock, and catches prey that are flushed by the treeshrew. The alliance is driven, and perhaps engineered by drongos, who seek out the treeshrews, and are instrumental in the sparrowhawks' detection of the treeshrews. The two bird species feed on insects and geckos flushed by the treeshrews during their intense feeding bouts. Treeshrews seem to tolerate sparrowhawks only in the presence of drongos or when they are in pairs. The choice of the raptor to join the association is intriguing; particular environmental resource states may drive the evolution of such behavioural strategies. Although foraging benefits seem to drive this association, predator avoidance also influences the kind of associations that occur, suggesting that strategies driving the formation of flocks may be complex and context dependent with varying benefits for different actors.      

Reference

Oommen, M.A. & K. Shanker (in press) Shrewd alliances: mixed foraging associations between treeshrews, greater racket tailed drongos and sparrowhawks on Great Nicobar Islands, India. Biology Letters

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Picture Credits


Nicobar treeshrew - Manish Chandi
Greater racket-tailed drongo - Amod Phadke (Oriental Bird Images)



© Kartik Shanker, 2012