Because of their wide latitudinal distribution, the races of the White-crowned Sparrow (Zonotrichia leucophrys) offer significant opportunities for comparative studies of the adaptive aspects of annual reproductive cycles and the mechanisms by which they are controlled. Of substantial interest among these races is 2. 2. pugetensis, a short-distance migrant whose breeding area (ca. 40-50"N) lies on the Pacific seaboard of North America between that of the highly migratory 2. 1. gambelii (ca. 50-70"N) and that of the sedentary 2. 1. nuttalli (ca. 35-40"N). The shortest migratory route of pugetensis may be considerably less than 500 km; the longest may approach 1900 km. Both the annual photoperiodic environment of pugetensis and its photoperiodic responses differ from those of the two related taxa (see Farner and Lewis 1973; Lewis 1971, 1975). Furthermore, pugetetis and nutialli, which form a cline (Banks 1964; Cortopassi and Mewaldt 1965), typically rear two or more broods per season (Banks 1959; Blanchard 1941), whereas gambelii appears to be obligately single-brooded (King et al. 1966). The present paper is the first of two that deal with the temporal organization of reproduction and its control in 2. 1. pugeteusis. In this paper, the breeding-season phenology and associated physiological and behavioral cycles are described and analyzed as a basis for experimental investigations of the mechanisms that control these functions. STUDY AREAS AND METHODS STUDY AREAS Camano Island (Island County, Washington), the principal study area, is a well-defined physiographic unit of 12,000 ha that lies in the Puget Sound lowland of western Washington, immediately west of the mainland between 48"3' and 48"16' N. It is about 24 km long and 1.5-11 km wide. Z. 1. pugetensis breeds on the island wherever suitable habitat occurs, from sea