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Echolocation in Free-Flying Atiu Swiftlets (Aerodramus sawtelli)

James H. Fullard, Robert M. R. Barclay and Donald W. Thomas
Biotropica
Vol. 25, No. 3 (Sep., 1993), pp. 334-339
DOI: 10.2307/2388791
Stable URL: http://www.jstor.org/stable/2388791
Page Count: 6
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Echolocation in Free-Flying Atiu Swiftlets (Aerodramus sawtelli)
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Abstract

Vocalizations of wild Atiu Swiftlets (Aerodramus sawtelli Holyoak 1974) were recorded as they entered and exited their roost/nesting cave on Atiu Island in the Cook Islands. The echolocation calls of the Atiu Swiftlet resemble those of other Aerodramus spp. in their short durations (1-3 msec). peak frequencies (6-7 kHz) and broad bandwidths (3-10 kHz) but are emitted as distinct single pulses rather than the double or multiple clicks typical of most swiftlets. Spectral analyses indicate that the birds do not adjust the peak frequencies of their calls as they fly within the cave and we suggest the bird does not systematically structure the frequency content of its calls. Birds decrease their interpulse periods upon entering the cave and increase them upon exiting, presumably in response to differing light levels. As they land at their roost/nest site, birds emit a train of low interpulse period calls that is occasionally followed by a vocalization that we suggest serves as an announcement to other birds on or near the nests.

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