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Ronald W. Summers, Alastair Grieve, Diet, Feeding Behaviour and Food Intake of the Upland Goose (Chloephaga picta) and Ruddy-Headed Goose (C. rubidiceps) in the Falkland Islands, Journal of Applied Ecology, Vol. 19, No. 3 (Dec., 1982), pp. 783-804
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Summers et al. (1982) studied this question.
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