Meeting Abstract

90.1  Wednesday, Jan. 7  Ontogeny of locomotor performance in a ground bird JACKSON, B.E.*; DIAL, K.P.; Univ. of Montana; Univ. of Montana brandon.jackson@mso.umt.edu

Due to post-natal predation pressure many juvenile animals face a developmental tradeoff between escape ability and investment in other systems. In birds these tradeoffs are unique because birds transition through hindlimb- to flap-running to wing-dominated locomotion to execute their escape. Early reliance on hindlimbs is compulsory until their diminutive wings can generate aerodynamic power, making young ground birds particularly vulnerable. This is the first study for any animal of the ontogeny of flap-based locomotion and the 3-D movements of wings. Using four synchronized high-speed video cameras we recorded the escape behavior of developing Chukars (Alectoris chukar). Wing-assisted incline running (WAIR) and controlled flapping descent (CFD) performance approach adult levels when the birds are ~10% of adult mass at ~20 days post hatching (dph). We define three stages of locomotor development. In stage I (1-7 dph) birds use assymmetrical flapping, quadrupedal crawling, have high wing-loading (WL 162±14 Nm^-2), low wingbeat frequency (f, 14±1.4 Hz) and stroke amplitude (AMP, 90±9°), but global stroke angle (SA 106±6°) and angle of attack (AoA 42±4°) approach adult values during WAIR, and they have high falling acceleration (9.1±0.1 ms^-2). In stage II (8-19 dph), birds flap symmetrically and have lower WL (69±4 Nm^-2), while AMP (141±4°), f (21±0.8 Hz), SA (106±3°) and AoA (44±2°) approach adult values. WL decreases (min: 62±1.2 Nm^-2) until stage III (20 dph-adult) when birds can ascend 90° and transition to level flight from a fall. WAIR and CFD provide transitional adaptive value to incipient wings and reduce the potential constraints of the hindlimb-forelimb developmental trade-off. Funded by NSF.