A functional analysis of the primary upstroke and downstroke muscles in the domestic pigeon (Columba livia) during flight.

In domestic pigeons (Columba livia), the electrical activity of the major depressor muscle of the wing, the pectoralis (pars thoracicus), beings in late upstroke well before the wing begins its downstroke excursion. The two architecturally distinct heads of the pectoralis, the sternobrachialis and the thoracobrachialis, are differentially recruited during take-off, level flight and landing. In addition to wing depression, the sternobrachialis protracts the humerus and the thoracobrachialis retracts the humerus. At the point of transition from wing upstroke to downstroke, the pectoralis EMG signal typically exhibits a reduction in amplitude. The supracoracoideus, in addition to an expected EMG associated with wing elevation, is co-activated with the pectoralis about 50% of the time.