Seasonal changes in crop content of the Svalbard Ptarmigan Lagopus mutus hyperboreus |
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| Authors: | SIGMUND UNANDER ATLE MORTENSEN ARVE ELVEBAKK |
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| Institution: | Sigmund Unander, Norsk Polarinstitutt, Rolfstangveien 12, 1330 Oslo Luflhavn, Norway;Atle Mortensen, Department of Arctic Biology and Institute of Medical Biology, University of Tromsø, N-9001 Tromsø, Norway;Arve Elvebakk, Institute of Biology and Geology, University of Tromsø, N-9001 Tromsø, Norway;'February 1985 (revised May 1985). |
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| Abstract: | Crop contents of Svalbard Ptarmigan have been examined. For chicks younger than 25 days the crops contained almost exclusively bulbils of Polygonum viviparum . High incidence of this food item was also found in crops from adult birds during late summer and autumn (July-October). Midwinter (November-February) crops contained a mixture of plant species dominated by herbs like Saxifraga oppositifolia and S. cespitosa , but with a significant contribution from Salix polaris . The proportion of 5. polaris increased throughout the winter and became highly dominant in spring (May-June). During all seasons the birds ingested plant parts of high nutritional value. The change in crop content from P. viviparum to 5. polaris via different herbs was associated with a decrease in the content of crude protein from 20–25% in July-August to about 16% in March-April, and a corresponding increase in crude fibre from about 10% to about 15%. The content of inorganic constituents (P, Mg, Ca, K, Na) varied insignificantly with season and was fairly high. |
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