Functional implications of the intertarsal joint shape in a terrestrial ( C oturnix coturnix ) versus a semi‐aquatic bird ( C allonetta leucophrys )

As birds have a diversity of locomotor behaviors, their skeleton is subjected to a variety of mechanical constraints (gravitational, aerodynamic and sometimes hydrodynamic forces). Yet, only minor modifications in post‐cranial skeleton shape are observed across the diversity of avian species in comparison with other vertebrates. The goal of this study was to explore potential morphological adjustments that allow locomotion in different habitats in A natidae. Specifically, we compared a strictly terrestrial bird, the common quail C oturnix coturnix , and a semi‐aquatic bird, the ringed teal C allonetta leucophrys , to explore whether their anatomy reflects the constraints of locomotion in different habitats (water vs. land). We compared the tibiotarsus and the tarsometatarsus shape between the two species using a geometric morphometric approach. Our data illustrate distinct differences between species with a more medially oriented intertarsal joint in the ringed teal than in the common quail, which may be linked to the kinematics of walking and paddling. This study lays the foundations to understand the functional requirements for moving in both terrestrial and aquatic environments in A natidae, and suggests morphological characteristics of the bird hindlimb skeleton that may help to predict the motions it is capable of.