Postnuptial Molt and Its Relation to Reproductive Cycle and Body Weight in Mountain White-Crowned Sparrows (Zonotrichia leucophrys oriantha)

Abstract

The body of information available on the relationship of postnuptial molt to reproductive functions indicates that, in general, these events are separated in time in birds that have altricial young. This is true of those that live in the tropics as well as the temperate zone, regardless of whether they are migratory or nonmigratory (

Energetics and Nutrition of Molt

“…Maintaining low body masses may also minimize maintenance costs (Ankney 1979). In many small birds, body mass increases gradually through the period of molt (e.g., Hussell1972 ;Payne 1972;Chilgren 1977;Mewaldt and King 1977;Dhondt and Smith 1980;Orell and Ojanen 1980;Rimmer 1988) and, depending on the timing of their annual cycles, premigratory fattening may begin before completion of the molt (Nisbet 1967;Morton and Welton 1973;Jehl1987;Morton and Morton 1990). These increases in body mass result partly from increases in protein and lipid, but also often reflect increases in body water contents that are associated with the expansion of the circulation needed for nurturing the growing feather and pulp.…”

Prebasic molt of the northern oriole

“…R,). Tail (Stresemann and Stresemann 1966 for ASY male northern orioles to molt after the females, however, contrasts with that reported in other icterids (Selander 1958) and passerines (Niles 1972;Morton and Welton 1973;Verbeek 1973). Middleton (1977) suggested that males usually molt before females, possibly because the testes degenerate slightly earlier than the ovaries.…”

“…Other workers have found that at least a slight increase in body weight occurs during prebasic molt of migratory passerines (see Morton and Welton 1973). They have attributed this increase generally to an increase in lean dry weight, fat, or water content.…”

“…They have attributed this increase generally to an increase in lean dry weight, fat, or water content. Morton and Welton (1973) contended that the 25% increase in body weight they found during molt of a high-altitude nesting race of the white-crowned sparrow (Zonotvichia leucophr-ys oviuntha) was due mostly to fat accumulation. They suggested Can.…”

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“…Some field evidence indicates that rearing a brood affects the parents' futures. Body weights and fat or protein reserves of both males and females in some passerines decrease while they rear young (Payne, 1969;Ward, 1969;Fogden, 1972;Morton and Welton, 1973). Hussell (1972) found weights of female buntings rearing large broods to be less than those rearing small broods and suggested that parents of large broods may survive and breed less well in later years.…”