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Seasonal Changes in Body Composition and Crop Content of Spitzbergen Ptarmigan Lagopus mutus hyperboreus
A. Mortensen, S. Unander, M. Kolstad and A. S. Blix
Ornis Scandinavica (Scandinavian Journal of Ornithology)
Vol. 14, No. 2 (Jun., 1983), pp. 144-148
Stable URL: http://www.jstor.org/stable/3676018
Page Count: 5
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The seasonal changes in body composition and crop content of Spitzbergen ptarmigan Lagopus mutus hyperboreus, shot at Svalbard were studied. A remarkable deposition of fat started in August and peaked in October/November, when dissectible fat made up as much as 32 and 24% of body weight in adults and juveniles, respectively. The variations in body fat neatly followed the changes in photo-period, but bore no relationship on climatic conditions. Thus, consumption of fat stores started at the onset of the continuous winter night, and they were exhausted in February when the sun-light reappeared, although winter conditions at this location continue into the month of May. The mobilization of body fat in the dark period was accompanied by a considerable drop in crop content, indicating a decrease in food intake at this time of the year. Fat free body weight of the birds only underwent minor variations throughout the year. It is suggested that the fat deposition in Spitzbergen ptarmigan serves the purpose of making these birds less dependant on food intake in the midst of the high-arctic winter, when the dark period makes access to food a matter of chance.
Ornis Scandinavica (Scandinavian Journal of Ornithology) © 1983 Nordic Society Oikos