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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. 相似文献
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Studies of wild and captive Willow and Svalbard Ptarmigan hens have allowed us to estimate the daily energy cost during incubation. It was similar for the two species, varying between 70-85 kcal per day depending on number of eggs, nest insulation, ambient temperature, number of foraging periods and total time spent away from the nest. Daily energy cost during incubation was 15 - 20% above resting metabolic rate in non-incubating hens but only 45 - 55% of that in free-living non-incubating hens. Incubating hens reduced their energy expenditure through high nest attentiveness. A reduction in food intake during incubation led to loss in body weight. 相似文献
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