Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus
Swifts regularly spend the night flying at high altitude. From previous studies based on tracking radar observations, we know that they stay airborne during the night and prefer to orient themselves into the wind direction with an increased angular concentration with increasing wind speed. In this s...
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fthighwire:oai:open-archive.highwire.org:jexbio:205/7/905 2023-05-15T14:17:16+02:00 Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus Bäckman, Johan Alerstam, Thomas 2002-04-01 00:00:00.0 text/html http://jeb.biologists.org/cgi/content/short/205/7/905 en eng Company of Biologists http://jeb.biologists.org/cgi/content/short/205/7/905 Copyright (C) 2002, Company of Biologists Research Article TEXT 2002 fthighwire 2015-02-28T20:02:32Z Swifts regularly spend the night flying at high altitude. From previous studies based on tracking radar observations, we know that they stay airborne during the night and prefer to orient themselves into the wind direction with an increased angular concentration with increasing wind speed. In this study, we investigated the orientation relative to the wind of individual swifts by frequency (discrete Fourier transform) and autocorrelation analysis based on time series (10s intervals) of the angle between the swifts' heading and the wind direction for radar trackings of long duration (9-60 min). The swifts often showed a significant harmonic oscillation of their heading direction relative to the wind, with a frequency mostly in the range 1-17 mHz, corresponding to cycle periods of 1-16 min. The swifts also sometimes performed circling flights at low wind speeds. Wind speed ranged from 1.3 to 14.8 m s-1, and we expected to find different patterns of orientation at different wind speeds, assuming that the swifts adapt their orientation to avoid substantial displacement during their nocturnal flights. However, oscillatory orientation was found at all wind speeds with variable frequencies/periods that did not show any consistent relationship with wind speed. It remains to be shown whether cyclic heading changes are a regular feature of bird orientation. Text Apus apus HighWire Press (Stanford University) |
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HighWire Press (Stanford University) |
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English |
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Research Article |
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Research Article Bäckman, Johan Alerstam, Thomas Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus |
topic_facet |
Research Article |
description |
Swifts regularly spend the night flying at high altitude. From previous studies based on tracking radar observations, we know that they stay airborne during the night and prefer to orient themselves into the wind direction with an increased angular concentration with increasing wind speed. In this study, we investigated the orientation relative to the wind of individual swifts by frequency (discrete Fourier transform) and autocorrelation analysis based on time series (10s intervals) of the angle between the swifts' heading and the wind direction for radar trackings of long duration (9-60 min). The swifts often showed a significant harmonic oscillation of their heading direction relative to the wind, with a frequency mostly in the range 1-17 mHz, corresponding to cycle periods of 1-16 min. The swifts also sometimes performed circling flights at low wind speeds. Wind speed ranged from 1.3 to 14.8 m s-1, and we expected to find different patterns of orientation at different wind speeds, assuming that the swifts adapt their orientation to avoid substantial displacement during their nocturnal flights. However, oscillatory orientation was found at all wind speeds with variable frequencies/periods that did not show any consistent relationship with wind speed. It remains to be shown whether cyclic heading changes are a regular feature of bird orientation. |
format |
Text |
author |
Bäckman, Johan Alerstam, Thomas |
author_facet |
Bäckman, Johan Alerstam, Thomas |
author_sort |
Bäckman, Johan |
title |
Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus |
title_short |
Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus |
title_full |
Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus |
title_fullStr |
Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus |
title_full_unstemmed |
Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus |
title_sort |
harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift apus apus |
publisher |
Company of Biologists |
publishDate |
2002 |
url |
http://jeb.biologists.org/cgi/content/short/205/7/905 |
genre |
Apus apus |
genre_facet |
Apus apus |
op_relation |
http://jeb.biologists.org/cgi/content/short/205/7/905 |
op_rights |
Copyright (C) 2002, Company of Biologists |
_version_ |
1766289147541061632 |