FORAGING BEHAVIOUR OF THE DUNE LARK

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Abstract
Cox, George W. 1983. Foraging behaviour of the Dune Lark. Ostrich 54:113-120. Foraging behaviour of the Dune Lark Mirafra erythrochlamys was studied in a dune environment at the Namib Research Institute, Gobabeb, South West Africa/Namibia in August 1981. Birds foraged for a total of 7 h per day in morning and afternoon periods separated by 3 h of inactivity during the warm midday. The birds exploited a distinctive series of vegetational belts dominated by three grasses. About two-thirds of total foraging time was spent in zones of dead and dormant grasses where seeds were sought by excavating small craters in the sand with the bill. Simples taken in the field, and simulations of bill-cratering behaviour in the laboratory, showed that this behaviour displaced seed-poor surface sand and exposed deeper, seed-rich layers. Birds formed small flocks when foraging for seeds in these zones. The remaining third of foraging time was spent in zones with large, live grass clumps, where insects were sought. Insect foraging was concentrated at the start and end of each activity period, but was most intense just before the midday period of inactivity when temperatures approached 30°C. Rough calculations of energy and water balance suggest that the larks are unable to maintain water balance under the observed conditions on seed food alone, and that this balance is achieved by feeding on insects. It is predicted that relative seed and insect foraging effort varies with temperature and season, as also suggested by limited published data on stomach contents in summer and winter.

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