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Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus.

Bäckman, Johan LU and Alerstam, Thomas LU (2002) In Journal of Experimental Biology 205(Pt 7). p.905-910
Abstract
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... (More)
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. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Experimental Biology
volume
205
issue
Pt 7
pages
905 - 910
publisher
The Company of Biologists Ltd
external identifiers
  • wos:000175056900003
  • scopus:0036332111
ISSN
1477-9145
language
English
LU publication?
yes
id
c8726a1d-41ff-4b20-a939-8e9cc4039dd1 (old id 107221)
alternative location
http://jeb.biologists.org/cgi/content/abstract/205/7/905
date added to LUP
2007-06-25 07:51:54
date last changed
2017-10-22 03:40:23
@article{c8726a1d-41ff-4b20-a939-8e9cc4039dd1,
  abstract     = {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.},
  author       = {Bäckman, Johan and Alerstam, Thomas},
  issn         = {1477-9145},
  language     = {eng},
  number       = {Pt 7},
  pages        = {905--910},
  publisher    = {The Company of Biologists Ltd},
  series       = {Journal of Experimental Biology},
  title        = {Harmonic oscillatory orientation relative to the wind in nocturnal roosting flights of the swift Apus apus.},
  volume       = {205},
  year         = {2002},
}