Morphological values of three traits of adult male hummingbirds.

We compiled measurements of three traits in adult males: body mass, wing chord (i.e., closed wing-length), and length of exposed culmen (Graham et al. 2012). The three traits represent important morphological interfaces for hummingbird flight, physiology, feeding and behavior. Body mass is related to thermoregulatory adaptations to high elevation habitats, as well as aggressive interactions among territorial species (Altshuler and Dudley 2002; González-Gómez et al. 2011a; González-Gómez et al. 2011b). Wing chord is a component of hovering flight, which becomes more difficult at high elevations due to lower air density (Altshuler et al. 2004; Stiles et al. 2005). Bill length is associated with resource use, foraging efficiency, and the matching between bill lengths and corolla lengths in hummingbird pollinated plants (Feinsinger et al. 1979; Smith et al. 1996; Temeles et al. 2002). These three traits show a predicted trait environment-relationship when all species in an assemblage are considered: body mass increases with elevation, wing chord increases with elevation and bill length decreases with elevation (high elevation flowers have short corollas; (Stiles 2008)). All three traits can be well described by a Brownian motion model of trait evolution, indicating phylogenetic signal (Blombergs K ~ 1 for all traits; Graham et al. 2012).