Meeting Abstract
Locomotor behavior and wing use among transitional forms of birds has only recently been evaluated. Recruitment of rudimentary and/or compromised wings appears common among extant species during: (1) ontogeny (development of wings), (2) molting (seasonal loss and regeneration of feathers), (3) maturation (increase in body mass relative to constant wing size) and (4) flight degradation (semi-flightlessness, triggered by reduction of predation pressure). Therefore, all birds undergo transitional anatomical changes that result in the reduction and/or augmentation of wing use. I survey most avian extant clades to better understand how species employ rudimentary wings during locomotion. In some cases, juveniles are more flight-capable than the adults (e.g., Giant coot and Brush Turkey) resulting from significant changes in wing loading during maturation. During changes in wing development (1-4 above), birds recruit their transitional wings, be it for coordination/balance or locomotion, by flapping their forelimbs rather than glide. Avian clades that invest heavily in their hindlimb apparatus (e.g., Galliformes, Anseriforms, etc.,) appear predisposed to lose flight if released from predation pressure but only if they can acquire food year-round without flight. Whereas, avian species that heavily invest in their forelimbs at the expense of hindlimbs (e.g., Apodiformes), have not been observed to evolve semi-flightless or flightless forms. An overarching trend among extant avian species during the waxing and waning of wings is flapping behavior (not gliding) and the simultaneous recruitment of hindlimbs to assist transitional wings.
