Meeting Abstract

43.5  Monday, Jan. 5  Forelimb skeletal kinematics of chukar partridges (Alectoris chukar) during wing-assisted incline running and ascending flight BAIER, DB*; GATESY, SM; DIAL , KP; Brown University; Brown University; Montana State University David_Baier@brown.edu

The origin of avian flight remains controversial. Recent studies have shown that birds use their wings not only for flight, but also when scrambling up steep inclines (ca. 60 to 90+) to an elevated refuge. Vulnerable fledglings can employ Wing-Assisted Incline Running (WAIR) to access otherwise inaccessible escape routes. Thus, WAIR presents a sound ecological basis for how forelimbs evolved into proto-wings and then into flight capable wings. Wing-stroke excursion differs superficially between WAIR and flight, but the underlying skeletal motions are masked by feathers and skin. We used the dual X-ray of the newly developed XROMM system (X-ray Reconstruction of Moving Morphology) to quantify 3-D skeletal kinematics in Chukar Partridges during WAIR up a 70 ramp to a perch and during ascending flight along the same trajectory. CT models of shoulder girdle and wing elements were positioned and oriented to match the two video views to measure shoulder, elbow and wrist joint motion. Overall, the patterns of motion are similar for all joints during both WAIR and ascending flight, but vary in a few key aspects. Glenohumeral elevation/depression ranges from ca. 80 to -5 during flight but depression is truncated to about 30 during WAIR. Glenohumeral pronation during flight is ca. 20 greater at the downstroke/upstroke transition. Wrist flexion and extension are also greater during ascending flight. Elbow motion is similar between both WAIR and flight.