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Résumé :
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1 1500 weights of tits were obtained in the winter 1951–52 and in November and December 1952. 2 On average the birds weighed least in the early morning and most just before going to roost in the late afternoon. The increase in weight slackened off around mid-day, corresponding with a decrease in feeding. 3 The average weights were inversely correlated with air temperature, owing to increased feeding on cold days. 4 Blue, Great and Coal Tits were on average heaviest in December (or possibly November) and weights then fell gradually. 5 It is suggested that the increase in weight by passerine birds in early winter is an adaptation for a potential shortage of food later.
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