The exploitation of intertidal food resources in Inhaca Bay, Mozambique, by shorebirds and humans

Abstract

The intertidal areas on Inhaca island provide important food resources for shorebirds as well as the local population. Average bird density is 2–6 individuals/ha during summer, decreasing to 0.3 in winter, which is one of the lowest records for the African coasts. Whimbrels Numenius phaeopus and curlew sandpipers Calidris ferruginea are the most abundant species. Total littoral fauna consumption is low, estimated at 2.5 g ash-free dry weight/m 2/year, of which only 18% is harvested by humans. Species preferences, numbers and weights are given for humans who collect invertebrates. The influence of human presence on bird behaviour is measured, using Minimal Approach Distances (MAD), foraging activity changes and people-bird abundance correlation. Larger birds have longer MADs and their foraging activity decreases earlier when approached by humans. The large, territorial whimbrel is most influenced by human presence and this interference competition is responsible for a 34% reduction of foraging time.