THE ANNUAL MOLT CYCLE OF BRANTA-CANADENSIS-INTERIOR IN RELATION TO NUTRIENT RESERVE DYNAMICS

During July 1984-February 1987, we measured the duration and seasonal changes in intensity of prebasic molt in Canada Geese (Branta canadens is interior) of the Mississippi Valley Population (MVP). Temporal and geographic variations in molt intensity were examined in relation to l ipid and protein reserve dynamics and the chronology of annual events. Wing- and body-molt intensities were greatest before fall migration, but limited body molt overlapped migration and continued into fall. Fi nal stages of molt progressed with declining intensity through winter. Only the nesting season (May-June) was entirely free of molt. Molt in individual geese may have required greater-than-or-equal-to 8 months (July-March) in at least 60% of the population. Temporal and geographi c variation in molt intensity were associated with differences in lipi d mass, but carcass protein had little apparent relationship with molt intensity. There was no evidence of net catabolism of nutrient reserv es between hatching, wing molt, and post-molting periods. Lipid masses of breeding females and non-breeding geese declined during wing molt. Protein masses declined during wing molt only in breeding and non-bre eding males, due to atrophy of breast muscles associated with flightle ssness. Seasonal changes in molt intensity and lipid reserves indicate d that geese allocated energy to emphasize molting before fall migrati on, and nutrient reserve deposition thereafter. The largest nutritiona l costs of molting probably were incurred during July-November. We pro pose that rate, intensity, and duration of body molt were influenced b y the amount of productive energy geese were able to allocate to feath er growth, without compromising replenishment of nutrient reserves aft er breeding or the deposition of reserves before winter. The simple, s ingle molt of Canada Geese provides greater latitude in adjusting nutr itional demands to environmental conditions than is possible for ducks that molt twice annually.