RELATIVE COSTS OF PREBASIC AND PREALTERNATE MOLTS FOR MALE BLUE-WINGED TEAL

We compared masses of definitive basic and alternate plumages of male Blue-winged Teal (Anas discors) to evaluate the hypothesis that nutrit ional investments in basic and alternate plumages are related to the d uration that plumages are worn and to assess the relative costs of pre basic and prealternate molts. Because these plumages are worn by males for approximately equal durations, we predicted that masses of the ba sic and alternate body plumages would be similar. To assess nutritiona l stress (demands greater than available resources) associated with mo lt, we examined the relation between remigial length and structural si ze and compared predicted and observed plumage masses of Blue-winged T eal and other ducks. If birds were nutritionally challenged during rem igial molt, then we predicted remigial length would be influenced by n utrition lather than size, and remigial length and size would be unrel ated. Alternate body plumage of male Blue-winged Teal weighed about 10 % more than the basic body plumage; however, masses of both plumages w ere less than that predicted on the basis of lean body mass. We argue that deviations between observed and predicted plumage masses were rel ated to factors other than nutrition. Further remigial lengths were si gnificantly, albeit weakly, related to structural size. We therefore c oncluded that, although the potential for molt-induced stress may be g reatest in small-bodied waterfowl species, there was no clear evidence that molting male Blue-winged Teal were nutritionally stressed.