Comparison of daily energy expenditure of greater snow geese between two habitats

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Abstract
We estimated the daily energy expenditure (DEE) of greater snow geese (Anser caerulescens atlanticus) on their St. Lawrence River estuary spring staging ground using time budget data. We compared DEE between two habitats: the traditionally occupied freshwater Scirpus-dominated marsh (SCI), and the recently invaded Spartina-dominated salt marsh (SPA). As greater snow geese staging at SCI have been found to accumulate larger fat reserves in the spring than those staging at SPA, we sought to explain these differences in diverging DEE patterns between the two habitats. We found that geese spent 42% more time (and energy) feeding in the marsh at SCI, but spent 61% less energy feeding in the field than at SPA. The energy spent in other activities was similar in both habitats. However, during the 6-week staging period, DEE was lower by only 4.7% at SPA (1613 kJ/day; 2.3 × basal metabolic rate (BMR) when compared with SCI (1689 kJ/day; 2.5 × BMR). This difference in DEE cannot account for the habitat-based differences in prebreeding fattening, and alternative hypotheses are examined.