Dummy eggs were added to naturally incubated clutches of Greater Snow Geese (Chen caerulescens atlantica), an arctic-nesting species, in order to evaluate egg temperature during laying and incubation, and factors influencing egg cooling rate during female recesses. As laying progressed, both nest attentiveness by females and egg temperature progressively increased. Although the time spent at nest after laying the penultimate egg was relatively high (69% vs. 91% during incubation), mean egg temperature was still 5.7°C lower than during the early incubation period. This suggests that little embryonic development began before clutch completion. Thereafter, egg temperature averaged 37.1 ± 0.1°C during periods where females were present, a value that decreased only slightly when incubation recesses are included (36.8°C). This is a high temperature in comparison to other arctic-nesting geese. A modest increase (1.7°C) in mean egg temperature was observed as incubation progressed, but egg temperature was not influenced by clutch size or by the laying date of the first egg. During recesses lasting 24.7 ± 1.3 min on average, egg temperature dropped by 2.8 ± 0.3°C, at an instantaneous rate of 0.23 ± 0.02°C hr−1 °C−1. Cooling rates increased under windy conditions and decreased with high solar radiation, but were little affected by air temperature.
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Vol. 102 • No. 2