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Flight speeds among bird species: allometric and phylogenetic effects. PLoS Biol (2007)
| Citations: | 12 - 0 self |
BibTeX
@MISC{Alerstam07flightspeeds,
author = {Thomas Alerstam and Per G. P. Ericson and Olof Hellgren},
title = {Flight speeds among bird species: allometric and phylogenetic effects. PLoS Biol},
year = {2007}
}
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Abstract
Flight speed is expected to increase with mass and wing loading among flying animals and aircraft for fundamental aerodynamic reasons. Assuming geometrical and dynamical similarity, cruising flight speed is predicted to vary as (body mass)1/6 and (wing loading)1/2 among bird species. To test these scaling rules and the general importance of mass and wing loading for bird flight speeds, we used tracking radar to measure flapping flight speeds of individuals or flocks of migrating birds visually identified to species as well as their altitude and winds at the altitudes where the birds were flying. Equivalent airspeeds (airspeeds corrected to sea level air density, Ue) of 138 species, ranging 0.01–10 kg in mass, were analysed in relation to biometry and phylogeny. Scaling exponents in relation to mass and wing loading were significantly smaller than predicted (about 0.12 and 0.32, respectively, with similar results for analyses based on species and independent phylogenetic contrasts). These low scaling exponents may be the result of evolutionary restrictions on bird flight-speed range, counteracting too slow flight speeds among species with low wing loading and too fast speeds among species with high wing loading. This compression of speed range is partly attained through geometric differences, with aspect ratio showing a positive relationship with body mass and wing loading, but additional factors are required to fully explain the small scaling exponent of Ue in relation to wing loading. Furthermore, mass and wing loading accounted for only a limited proportion of the variation in Ue. Phylogeny was a powerful factor, in combination with wing loading, to account for the variation in Ue. These results demonstrate that
Keyphrases
flight speed bird specie phylogenetic effect plo biol body mass level air density low scaling exponent general importance similar result evolutionary restriction fast speed equivalent airspeed additional factor positive relationship dynamical similarity speed range limited proportion scaling rule bird flight speed powerful factor slow flight speed small scaling exponent fundamental aerodynamic reason geometric difference aspect ratio independent phylogenetic contrast bird flight-speed range
