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Flight speeds and climb rates of Brent Geese: mass-dependent differences between spring and autumn migration

Green, Martin LU and Alerstam, Thomas LU (2000) In Journal of Avian Biology 31(2). p.215-225
Abstract
Aerodynamic theories of bird flight predict that horizontal flight speed will increase with increasing load whereas vertical Eight speed will decrease. Horizontal flight speed for birds minimizing overall time on migration is predicted to be higher than flight speed for birds minimizing energy expenditure. In this study we compare flight speeds of Brent Geese Branta b. bernicla recorded by tracking radar and optical range finder during spring and autumn migration in southernmost Sweden, testing the above-mentioned predictions. Geese passing Sweden in spring are substantially heavier than in autumn and there might also be a stronger element of time-selection in spring than in autumn. Recorded airspeeds were significantly higher in spring... (More)
Aerodynamic theories of bird flight predict that horizontal flight speed will increase with increasing load whereas vertical Eight speed will decrease. Horizontal flight speed for birds minimizing overall time on migration is predicted to be higher than flight speed for birds minimizing energy expenditure. In this study we compare flight speeds of Brent Geese Branta b. bernicla recorded by tracking radar and optical range finder during spring and autumn migration in southernmost Sweden, testing the above-mentioned predictions. Geese passing Sweden in spring are substantially heavier than in autumn and there might also be a stronger element of time-selection in spring than in autumn. Recorded airspeeds were significantly higher in spring (mean 19.0 m s(-1)) than in autumn (mean 17.3 m s(-1)), the average difference bring slightly larger than predicted due to the mass difference alone. The effects on airspeed of wind, vertical speed, flock size and altitude were also analysed, but none of these factors could explain the seasonal difference in airspeed. Hence, the results support the hypothesis of mass-dependent flight speed adjustment. The difference between the two seasons was not large enough to corroborate the hypothesis of a stronger element of time-selection in spring, but this hypothesis cannot be rejected. Vertical flight speeds were lower in spring than in autumn, supporting a negative effect of load on birds' Right power margin. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Avian Biology
volume
31
issue
2
pages
215 - 225
publisher
Federation of European Neuroscience Societies and Blackwell Publishing Ltd
ISSN
0908-8857
DOI
10.1034/j.1600-048X.2000.310213.x
language
English
LU publication?
yes
id
10c6c46e-2d0a-4116-8d7a-04b8df1bce6d (old id 145991)
date added to LUP
2007-06-26 07:20:18
date last changed
2016-04-15 18:49:11
@article{10c6c46e-2d0a-4116-8d7a-04b8df1bce6d,
  abstract     = {Aerodynamic theories of bird flight predict that horizontal flight speed will increase with increasing load whereas vertical Eight speed will decrease. Horizontal flight speed for birds minimizing overall time on migration is predicted to be higher than flight speed for birds minimizing energy expenditure. In this study we compare flight speeds of Brent Geese Branta b. bernicla recorded by tracking radar and optical range finder during spring and autumn migration in southernmost Sweden, testing the above-mentioned predictions. Geese passing Sweden in spring are substantially heavier than in autumn and there might also be a stronger element of time-selection in spring than in autumn. Recorded airspeeds were significantly higher in spring (mean 19.0 m s(-1)) than in autumn (mean 17.3 m s(-1)), the average difference bring slightly larger than predicted due to the mass difference alone. The effects on airspeed of wind, vertical speed, flock size and altitude were also analysed, but none of these factors could explain the seasonal difference in airspeed. Hence, the results support the hypothesis of mass-dependent flight speed adjustment. The difference between the two seasons was not large enough to corroborate the hypothesis of a stronger element of time-selection in spring, but this hypothesis cannot be rejected. Vertical flight speeds were lower in spring than in autumn, supporting a negative effect of load on birds' Right power margin.},
  author       = {Green, Martin and Alerstam, Thomas},
  issn         = {0908-8857},
  language     = {eng},
  number       = {2},
  pages        = {215--225},
  publisher    = {Federation of European Neuroscience Societies and Blackwell Publishing Ltd},
  series       = {Journal of Avian Biology},
  title        = {Flight speeds and climb rates of Brent Geese: mass-dependent differences between spring and autumn migration},
  url          = {http://dx.doi.org/10.1034/j.1600-048X.2000.310213.x},
  volume       = {31},
  year         = {2000},
}