eWestern BirdsThe Quarterly Journal of Western Field Ornithologists
Vol. 31, No. 1
Western Field Ornithologists
Molt Cycles and Sequences in the Western Gull
Steve N. G. Howell, Chris Corben
ABSTRACT: We describe the molt cycle of the Western Gull (Larus occidentalis) in central California on the basis of field observations of unmarked birds. The Western Gull has one partial and one complete molt per year. The first and second partial molts span up to 7 or 8 months, subsequent prealternate molts about 4 to 6 months. The complete prebasic molt spans 5-6 months. We propose that the Western Gull exemplifies a pattern more widespread among large water birds: the first partial (“postjuvenal”) molt appears homologous with later prealternate molts, not with the prebasic molt, as considered previously.