Prey Escape Direction is Influenced by the Pivoting Displays of Flush-Pursuing Birds

Authors


Piotr Jabłoński, University of Arizona, ARLDN, 611 Gould-Simpson Bldg, Tucson, AZ 85 721, USA. E-mail: piotrjab@neurobio.arizona.edu

Abstract

Painted redstart, Myioborus pictus, and its congeners in Central and South America, belong to a small fraction of insectivorous flush-pursuing birds. Unlike most of the small insectivorous birds, which glean prey from substrates, the flush pursuers spread and pivot their conspicuously patterned tails and wings. This display triggers prey escape flights which are hypothesized to occur through visual stimulation of prey escape circuits [giant descending neuron cluster (GDNC) in Diptera] sensitive to the looming motion of an approaching bird, translational motion of a pivoting body with widely spread tail and contrast of the white-black plumage pattern. In this paper, data from field observations of redstarts and experiments with bird models show an increase in the frequency of prey escapes away from the strong visual stimulation of an open tail, and in the direction opposite to that of the horizontal translational motion present in the pivots. We discuss how the effect on prey escape direction may enhance prey interception capabilities of redstarts during aerial pursuits. Combined with an earlier study the results show that, unlike the movements of typical gleaner–foragers, the flush displays by redstarts affect prey escape direction in a manner that may facilitate prey tracking and capture by birds. Because the GDNs, which mediate escape initiation, are not sensitive to motion direction, we hypothesize that other neurons, in addition to the GDNs, are involved in influencing the direction of escape responses.

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