Comparative Foraging Efficiencies of Some Montane Sunbirds in Kenya

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Abstract
Four species of montane sunbirds, Nectarinia kilimensis, N. reichenowi, N. famosa and N. venusta, commonly feed together at flowers of the mint Leonotis nepetifolia in Kenya. Differences in bill dimensions of these sunbirds affect both the rate of nectar extraction and the proportion of available nectar that is removed from the flower. These results are consistent with the apparent fit between the bills and the length and curvature of the corolla, which affects the ability to reach nectar in a basal chamber partly protected by a corolla partition. Differences in body size affect foraging cost and render the species more similar, but not equivalent, with respect to rates of net caloric gain at this flower.