Meeting Abstract
Precocial ground birds fledge and acquire locomotor capacity early in ontogeny, sometimes shortly after hatching. However, anatomical structures used during locomotion appear late in development. For example, Chukar Partridges (Alectoris chukar) gain flight capacity approximately 18 to 20 days after hatching, but do not develop adult-like feathers or musculoskeletal apparatuses until two to three months of age. Similarly, Peafowl (Pavo cristatus) become flight-capable long before maturation of the flight apparatus. How do immature birds lacking the anatomical specializations of adults achieve adult-like levels of performance so early in ontogeny? Here, we integrate previous work with SIMM modeling (Software for Interactive Musculoskeletal Modeling) and cladistic ontogeny to track the development of locomotor morphology, function, performance, and behavior in precocial ground birds, using chukars as a case study. Our results demonstrate that developing chukars flap and produce aerodynamic forces during wing-assisted incline running (6 to 8 days post hatching) and flight (18 to 20 days post hatching) long before acquiring any of the specialized morphological features characteristic of adult birds (>45 days post hatching). Though younger birds have less aerodynamically effective feathers, less channelized skeletons, and smaller muscles than older birds, they appear to compensate for these limitations with a variety of anatomical and behavioral mechanisms. This complex developmental interplay between different anatomical features and whole body performance highlights the complexity of form-function relationships, and offers new insight into traditional views on the avian body plan and adaptations for flight.
