Seasonal changes in the metabolic properties of muscle in blue-winged teal, Anas discors

Abstract

The gizzard, flight, and leg muscles of blue-winged teal undergo changes in their aerobic and anaerobic metabolic capacities during the flightless (molting) period and just as the birds begin to regain the capability of flight. These changes do not appear to be solely the result of a use/disuse phenomenon. The aerobic capacity of the flight muscles decreases with the onset of flightlessness but increases dramatically just prior to regaining flight with little or no physical conditioning. Furthermore, the increase in the aerobic and anaerobic capacity of the leg muscles during the flightless period fails to totally mimic the changes known to occur with increased aerobic or anaerobic muscle use. The muscles of blue-winged teal appear to prepare, by some mechanism(s) as yet not elucidated, for their changed role at the onset of migration and molt, rather than simply responding to current muscle use.