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Daily variation in ambient temperature, body temperature, and heart rate during autumn (yellow, 1 Sep.–10 Oct.), migration period (red, 11 Oct.–20 Nov.), winter (blue, 21 Nov.–17 Feb.) and spring (green, 18 Feb.–11 Apr. 11). Plotted are hourly means across all three study years. Error bars represent 95% confidence intervals of the means and reflect the variation between days for the ambient temperature and between individuals for body temperature and heart rate.
