Breeding Biology of Pacific White-Fronted Geese

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Abstract
Nesting ecology of Pacific white-fronted geese (A. a. frontalis) was studied on a 9.9 km2 area on the Yukon-Kuskokwim (Y-K) Delta, Alaska, [USA], during 1977-1979. Availability of nesting habitat varied considerably among years because of differences in the time of snow and icemelt. Mean clutch size was 3.7 eggs in the late spring thaw year and 5.2 and 5.7 eggs in early snowmelt years. Peak (and duration) of nest initiation was 1-2 June (16 days) in the late spring and 15-18 May (20-21 days) during early spring. When nest sites were available early, the time interval between arrival and date of nest initiation closely approximated the time required for rapid yolk development. Whitefronts may be physiologically prevented from nesting earlier in such years. The duration of nest initiation was comparable to that of other goose species nesting on the Y-K Delta, but longer than for goose populations of several species nesting farther north or in the midcontinent. Overall, 68% of whitefront nests were in lowland habitat, 23% in intermediate habitat and 10% in upland habitat, but habitat use varied significantly between early and late years. Whitefronts most commonly nested on slough banks (55%), lake shores (23%) and grass-sedge meadows (11%). A quantitative description of vegetation associated with nest sites is given. Major causes of nest destruction were flooding (28%) and predation (9%). Nesting success over the 3-yr period averaged 62%.