Advanced

Optimal stopover decisions under wind influence: the effects of correlated winds

Weber, Thomas LU and Hedenström, Anders LU (2000) In Journal of Theoretical Biology 205(1). p.95-104
Abstract
Wind speed and direction have a significant effect on a flying bird's ground speed. Migrants are therefore expected to be sensitive to wind conditions and this should have consequences for optimal strategies of stopover and refuelling. Based on an earlier model of time-minimizing migration which includes wind condition, we investigate the consequences of the temporal correlation of wind conditions. Day-to-day changes in wind conditions are modelled with a two-state Markov process and an expression for the expected speed of migration is derived. The policy of the migrants is described by two parameters: a day t(g) when the birds start to leave whenever favourable conditions occur and a later day t(b) when they leave even in unfavourable... (More)
Wind speed and direction have a significant effect on a flying bird's ground speed. Migrants are therefore expected to be sensitive to wind conditions and this should have consequences for optimal strategies of stopover and refuelling. Based on an earlier model of time-minimizing migration which includes wind condition, we investigate the consequences of the temporal correlation of wind conditions. Day-to-day changes in wind conditions are modelled with a two-state Markov process and an expression for the expected speed of migration is derived. The policy of the migrants is described by two parameters: a day t(g) when the birds start to leave whenever favourable conditions occur and a later day t(b) when they leave even in unfavourable winds. The model predicts that in most cases departures should be close to the date which is predicted by a wind-free deterministic model and that the birds should never leave without wind assistance. Only if the probability that the condition remains the same on the following day is close to I should the birds leave even in unfavourable conditions shortly after the deterministic optimal date. If the transition matrix is highly asymmetrical, i.e. if it is very probable that unfavourable conditions remain and that favourable conditions will change into unfavourable, then the birds are predicted to start using good winds several days before the deterministic optimal date. An analysis of six years of wind data from two sites in Sweden shows that wind directions on successive days are in fact correlated in all years. (C) 2000 Academic Press. (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 Theoretical Biology
volume
205
issue
1
pages
95 - 104
publisher
Academic Press
external identifiers
  • scopus:0034616972
ISSN
1095-8541
DOI
10.1006/jtbi.2000.2047
language
English
LU publication?
yes
id
1e99a54b-88dc-4529-bdaf-62db84bce4bd (old id 146013)
date added to LUP
2007-06-26 12:37:41
date last changed
2017-11-05 04:27:01
@article{1e99a54b-88dc-4529-bdaf-62db84bce4bd,
  abstract     = {Wind speed and direction have a significant effect on a flying bird's ground speed. Migrants are therefore expected to be sensitive to wind conditions and this should have consequences for optimal strategies of stopover and refuelling. Based on an earlier model of time-minimizing migration which includes wind condition, we investigate the consequences of the temporal correlation of wind conditions. Day-to-day changes in wind conditions are modelled with a two-state Markov process and an expression for the expected speed of migration is derived. The policy of the migrants is described by two parameters: a day t(g) when the birds start to leave whenever favourable conditions occur and a later day t(b) when they leave even in unfavourable winds. The model predicts that in most cases departures should be close to the date which is predicted by a wind-free deterministic model and that the birds should never leave without wind assistance. Only if the probability that the condition remains the same on the following day is close to I should the birds leave even in unfavourable conditions shortly after the deterministic optimal date. If the transition matrix is highly asymmetrical, i.e. if it is very probable that unfavourable conditions remain and that favourable conditions will change into unfavourable, then the birds are predicted to start using good winds several days before the deterministic optimal date. An analysis of six years of wind data from two sites in Sweden shows that wind directions on successive days are in fact correlated in all years. (C) 2000 Academic Press.},
  author       = {Weber, Thomas and Hedenström, Anders},
  issn         = {1095-8541},
  language     = {eng},
  number       = {1},
  pages        = {95--104},
  publisher    = {Academic Press},
  series       = {Journal of Theoretical Biology},
  title        = {Optimal stopover decisions under wind influence: the effects of correlated winds},
  url          = {http://dx.doi.org/10.1006/jtbi.2000.2047},
  volume       = {205},
  year         = {2000},
}