Latitudinal Variation of Postnuptial Molt in Pacific Coast White-Crowned Sparrows

Abstract
The duration of postnuptial molt in the white-crowned sparrows (Zonotrichia leucophrys nuttalli and Z. l. pugetensis) decreases northward by an average of 2.6 days/degree of latitude between the southernmost (35.2.degree. north, molt duration 83 days) and northernmost (48.9.degree. north, 47 days) limits of the breeding range. Males begin molting earlier than females by as much as 2 wk. For both sexes the date on which molt begins is independent of latitude and is correlated with the end of nesting season.