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First published online September 5, 2008
Journal of Experimental Biology 211, 2976-2988 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.020057

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In-flight corrections in free-flying barn owls (Tyto alba) during sound localization tasks

Laura Hausmann^*, Dennis T. T. Plachta, Martin Singheiser, Sandra Brill and Hermann Wagner

Institute of Biology II, RWTH Aachen, Kopernikusstraße 16, 52074 Aachen, Germany

^* Author for correspondence (e-mail: laura{at}bio2.rwth-aachen.de)

Accepted 17 July 2008

Barn owls localize a stationary auditory target with high accuracy. They might also be able to hit a target that is intermittently moving while the owl is approaching. If so, there should be a critical delay before strike initiation, up to which the owl can adapt its flight path to a new stimulus position. In this study, this critical stimulus delay was determined in a three-dimensional free-flight paradigm. Barn owls localized a pulsed broadband noise while sitting on a perch in total darkness. This initial signal stopped with the owl's take-off and an in-flight stimulus (target sound), lasting 200 ms, was introduced at variable time delays (300–1200 ms) during the approximate flight time of 1300 ms. The owls responded to the in-flight signal with a corrective head and body turn. The percentage of trials in which correction turns occurred (40–80%) depended upon the individual bird, but was independent of the stimulus delay within a range of 800 ms after take-off. Correction turns strongly decreased at delays 800 ms. The landing precision of the owls, defined as their distance to the in-flight speaker, did not decrease with increasing stimulus delay, but decreased if the owl failed to perform a correction turn towards that speaker. Landing precision was higher for a short (50 cm) than for a large (100 cm) distance between the initial and the new target. Thus, the ability of barn owls to adapt their flight path to a new sound target depends on the in-flight stimulus delay, as well as on the distance between initial and novel targets.

Key words: barn owl, auditory, hearing, sound localization, flight, three-dimensional, target approaching, behavior

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