Post-Hatching Growth of the Pectoralis Muscle in Pigeon and Its Functional Implications.

The avian pectoralis muscle is responsible for the wing's downstroke, which provides birds with lift and thrust for flight. In the present study, architectural parameters were investigated through growth in the pigeon (Columba livia), an altricial bird species, from the ages of 4 days to 12 months, in order to assess the morphological changes and effects of increasing body mass. Muscle mass, fascicle length (FL), and physiological cross-sectional area (PCSA) increased with strong positive allometry. As an indicator of force production capacity, the PCSA increased 30-fold with the changes in body mass; it grew rapidly during the nesting period and post-fledging period into sexual maturity. The growth pattern of FL demonstrated a gradual increase before fledging and a marked increase after maturity. Taken together, the growth of the pectoralis was found to be dominated by a continuous increase in PCSA before maturity and subsequent increase in FL. These features were associated with the establishment and improvement of flight capability, and further revealed different strategies in maintaining relatively constant power prior to and after maturity. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc.