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Willow
Food quality
Digestion inhibitors
Intake rate
Herbivorous
bird
lagopus-lagopus-scoticus
ruffed grouse
mammalian herbivores
plant
chemistry
food selection
ptarmigan
digestion
wild
diet
constraints
Abstract:
Both the quality of food and the rate of food intake may influence an animal's food choice. We investigated the feeding choices of Chinese Grouse (Bonasa sewerzowi) among a group of trees/shrubs with similar morphologies but heterogeneous chemical compositions in a coniferous forest of the northeastern Qinghai-Tibet Plateau during two winters. The primary food was willow buds and twigs (foraging occurrence of 83%). The Kangding willow Salix paraplesia was most preferred, whereas the Sichuan willow S. hylonoma was most avoided, and feeding preference (foraging occurrence/food abundance) among the six main willow species was negatively correlated with the tannin content of the plant consumed rather than the protein, lipid, phosphorus, calcium, ash, fibre, or energy contents. The intake rates of dried biomass, energy, protein, fibre and tannin in different willow species were closely related to the bud sizes of these species. However, neither rate of intake nor total biomass acquired from a particular willow was related to the feeding preference of the Chinese Grouse. Therefore, we conclude that, rather than rate of food intake, the major evolutionary determinant of Chinese Grouse diet has been to maximise the intake of nutrients while simultaneously minimising the intake of digestion inhibitors.
