Migration, like any other ecological factor, shapes the morphology of birds. Most ecomorphological studies of migration have mainly considered external features (e.g. Cox 1968; Gaston 1974; Greenberg 1981). Winkler and Leisler (1992) partly overcame this deficit and related skeletal and myological measurements to migration in several passerine and non-passerine groups. Their main findings were: aspect ratio was higher in migrants in all groups studied; migration apparently set upper boundaries on the development of the hind limbs, especially in small birds. Similarly, Calmaestra and Moreno (1998a, 2000) analyzed forelimb muscles and skeletal elements that may distinguish migrant and resident passerine species by pairwise comparisons in 10, and 15, passerine genera. After correcting for phylogeny, they found, not surprisingly, that migrants possess larger sternal dimensions and longer coracoids, thus offering greater surface for attachment of the main flight muscles. Hindlimb elements were not related to migration but rather to habitat use.