Spring Accumulation of Fat by Greater Snow Geese in Two Staging Habitats

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Abstract
The influence of habitat on fat storage by greater snow geese (C. c. atlanticus) on their St. Lawrence River estuary [Canada]spring staging grounds was studied in 1979 and 1980. In all, 373 individuals (2 yr old and older birds only) were collected in 2 types of marsh during the 6 wk staging halt: the traditionally-occupied fresh-water, Scirpus-dominated marshes of the upper estuary (SCI) and in the newly-invaded (after the early 1960''s) salt-water, Spartina-dominated marshes (SPA) of the lower estuary. The birds reached SPA a few days later than SCI in early April, at which time their total fat reserves amounted to .apprx. 10% of their body weight. Fattening at SCI increased steadily throughout the staging period; at SPA it slowed markedly in females and stopped completely in males around the middle of the staging period. In birds departing for the arctic around May 18-20, the total fat reserves amounted to 19-20% of the body weight. Males departing from SCI carried 23% more fat on the average than those of SPA (P < 0.01); the difference amounted to 9% in females (P > 0.05). The geese could increase these reserves after leaving the St. Lawrence estuary and before reaching their high-arctic nesting grounds.