Flight muscles in falcons (Falconiformes, Falconinae): A quantitative approach

The family Falconidae has contrasting behaviors on its flight within the subfamilies. Falcons are primarily aerial predators requiring accuracy, high speed, and controlled movements during flight. Caracaras are generalists that seek food while walking and their flight is characterized as slow and erratic. We aimed to explore the muscle mass of the primary wing muscles in several species of Falconinae and to identify possible differences related to the role that these muscles perform during flight. We studied 34 wing muscles in 11 specimens of five species of falcons. The percentage of each muscle with respect to body mass was calculated as well as the total wing muscle mass. The search for differences between muscles of falcons and caracaras was analyzed using Bayesian statistical inference. Published data from Polyborinae were used for comparison. Five muscles were significantly different between both subfamilies mm. latissimus dorsi pars caudalis, biceps brachii, extensor carpi radialis, flexor digitorum superficialis, and extensor digitorum communis. The first two muscles were larger in Polyborinae, which could be useful to achieve more strength and stabilization. In falcons the last three muscles listed were larger, which might be associated with their fast and acrobatic flight. Variations in certain muscles generate, in turn, differences in function, which is reflected in their type of flight and its use. These findings reinforce the modular character of the locomotor system of birds whereby the regions involved in locomotion can have morphological peculiarities according to their lifestyle.