A Blog Around The Clock

Phylogeny vs. Aerodynamics in birds

A very interesting new paper was published today in PLoS Biology:

Flight Speeds among Bird Species: Allometric and Phylogenetic Effects by Thomas Alerstam, Mikael Rosen, Johan Backman, Per G. P. Ericson and Olof Hellgren:

Analysing the variation in flight speed among bird species is important in understanding flight. We tested if the cruising speed of different migrating bird species in flapping flight scales with body mass and wing loading according to predictions from aerodynamic theory and to what extent phylogeny provides an additional explanation for variation in speed. Flight speeds were measured by tracking radar for bird species ranging in size from 0.01 kg (small passerines) to 10 kg (swans). Equivalent airspeeds of 138 species ranged between 8 and 23 m/s and did not scale as steeply in relation to mass and wing loading as predicted. This suggests that there are evolutionary restrictions to the range of flight speeds that birds obtain, which counteract too slow and too fast speeds among bird species with low and high wing loading, respectively. In addition to the effects of body size and wing morphology on flight speed, we also show that phylogeny accounted for an important part of the remaining speed variation between species. Differences in flight apparatus and behaviour among species of different evolutionary origin, and with different ecology and flight styles, are likely to influence cruising flight performance in important ways.

Update: Grrrlscientist explains the study in plain English.


  1. #1 Markk
    July 18, 2007

    I’m having a hard time seeing the difference between “effects of body size and wing morphology” vs phylogeny. i see that for birds of similar structure (because they are taxonomically “phylogeny” related) relations are more straight forward and there are better extrapolations to speed. Still, that is because of similarity of body size and wing structure, no? Isn’t relatedness just a marker for metabolic and mechanical similarities?
    Plus I am surprised that power is not the primary factor taken into account – it certainly is in aerodynamic design.

    I like these kinds of approaches.

New comments have been temporarily disabled. Please check back soon.