Three-dimensional, high-resolution skeletal kinematics of the avian wing and shoulder during ascending flapping flight and uphill flap-running

PLoS One. 2013 May 15;8(5):e63982. doi: 10.1371/journal.pone.0063982. Print 2013.

Abstract

Past studies have shown that birds use their wings not only for flight, but also when ascending steep inclines. Uphill flap-running or wing-assisted incline running (WAIR) is used by both flight-incapable fledglings and flight-capable adults to retreat to an elevated refuge. Despite the broadly varying direction of travel during WAIR, level, and descending flight, recent studies have found that the basic wing path remains relatively invariant with reference to gravity. If so, joints undergo disparate motions to maintain a consistent wing path during those specific flapping modes. The underlying skeletal motions, however, are masked by feathers and skin. To improve our understanding of the form-functional relationship of the skeletal apparatus and joint morphology with a corresponding locomotor behavior, we used XROMM (X-ray Reconstruction of Moving Morphology) to quantify 3-D skeletal kinematics in chukars (Alectoris chukar) during WAIR (ascending with legs and wings) and ascending flight (AF, ascending with wings only) along comparable trajectories. Evidence here from the wing joints demonstrates that the glenohumeral joint controls the vast majority of wing movements. More distal joints are primarily involved in modifying wing shape. All bones are in relatively similar orientations at the top of upstroke during both behaviors, but then diverge through downstroke. Total excursion of the wing is much smaller during WAIR and the tip of the manus follows a more vertical path. The WAIR stroke appears "truncated" relative to ascending flight, primarily stemming from ca. 50% reduction in humeral depression. Additionally, the elbow and wrist exhibit reduced ranges of angular excursions during WAIR. The glenohumeral joint moves in a pattern congruent with being constrained by the acrocoracohumeral ligament. Finally, we found pronounced lateral bending of the furcula during the wingbeat cycle during ascending flight only, though the phasic pattern in chukars is opposite of that observed in starlings (Sturnus vulgaris).

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biomechanical Phenomena
  • Birds / physiology*
  • Bone and Bones / anatomy & histology
  • Bone and Bones / physiology*
  • Flight, Animal*
  • Shoulder / anatomy & histology
  • Shoulder / physiology*
  • Wings, Animal / anatomy & histology
  • Wings, Animal / physiology*

Grant support

Funding was provided by the National Science Foundation grant entitled "Ontogeny of Avian Locomotion: Aerodynamics, Skeletal Kinematics, and Neuromuscular Control", award number 0919799, the W.M. Keck Foundation grant entitled "A Proposal to Design and Build a Dynamic 3-D Skeletal Imaging System" and the NSF grant entitled "IDBR: Hardware and Software Development for 3D Visualization of Rapid Skeletal Motion in Vertebrate Animals", award number 0552051. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.