SEASONAL-CHANGES IN THE METABOLIC PROPERTIES OF MUSCLE IN BLUE-WINGEDTEAL, ANAS DISCORS

The gizzard, flight, and leg muscles of blue-winged teal undergo chang es in their aerobic and anaerobic metabolic capacities during the flig htless (molting) period and just as the birds begin to regain the capa bility 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 conditionin g. Furthermore, the increase in the aerobic and anaerobic capacity of the leg muscles during the flightless period fails to totally mimic th e changes known to occur with increased aerobic or anaerobic muscle us e. The muscles of blue-winged teal appear to prepare, by some mechanis m(s) as yet not elucidated, for their changed role at the onset of mig ration and molt, rather than simply responding to current muscle use.