Diet, feeding behaviour and food intake of the upland goose (Chloephaga picta) and ruddy-headed goose (C. rubidiceps) in the Falkland Islands.
Abstract
The diet of upland and ruddy-headed geese was composed mainly of Poa annua and P. pratensis. Leaf lengths of P. annua/pratensis eaten on 'greens' did not vary seasonally for upland geese and there was no significant difference in lengths taken by ruddy-headed and upland geese in winter. Berries, grass-seeds and green algae were eaten at certain seasons. Geese arrived on pastures shortly before sunrise and left shortly after sunset. Numbers varied little through the day. The two goose species had similar time activity budgets though the proportion of time allotted to some activities varied seasonally, e.g. in winter a greater proportion of the day was spent grazing compared with summer. The digestive efficiency of a captive upland goose fed on grass pellets was measured directly (by measuring input and output) and indirectly (using the cell wall material of the grass as an indigestible marker). The two methods gave similar results (25.8% and 25.3% respectively) indicating the accuracy of the latter method, which was then used for free-living geese. The organic matter digestive efficiencies of free-living geese varied from 27 to 34% on Poa greens for winter and summer. Faecal output was determined from frequency of defaecation and weights of faeces. This was converted to gross and net intakes using estimates of digestive efficiency. Gross intakes per day for male and female upland geese were 5100 kJ and 4000 kJ respectively, and 2600 kJ for ruddy-headed geese feeding on greens in winter. The corresponding net intakes were 1900 kJ, 1500 kJ and 900 kJ per day. The latter values were close to estimated daily energy requirements based on published equations. The feed value of goose faeces to sheep, which often eat them, was measured in terms of digestibility and nitrogen content. They had similar digestibility and nitrogen content to good-quality grass.