Feeding Habits and Diet Composition of the African Sacred Ibis in Selected Water-Logged Sites in Dar es Salaam, Tanzania

Abstract

The African Sacred Ibises Threskiornis aethiopicus are generalist birds that feed on many invertebrates and some vertebrates. However, the diet composition of local T. aethiopicus populations in wetland areas in Dar es Salaam Tanzania was unknown. Sacred Ibises from eight water-logged areas in Dar es Salaam City, Tanzania were studied to determine their feeding habits and diet composition using direct observations and molecular analysis of faecal samples. Snails species identified from sites frequented by T. aethiopicus included Lymnaea natalensis (61.62%), Melanoides tuberculatus (20.64%), Bulinus sp. (17.66%) and Anisus sp. (0.08%), while molecular analysis of the birds’ diet revealed presence of mostly non-native invasive molluscs (Physa acuta, Planorbella trivolvis and Radix natalensis), fungus (Candida parapsilosis) and protozoan ciliate (Vorticella striata). There was no significant association between bird and snail abundance (r = 0.2141, p > 0.05, ns) although snail diversity showed strong negative relationship (r = -0.7904, p < 0.05). Our findings indicate that the African Sacred Ibises do not preferentially feed on snails, but do so as part of their broader diet. The results confirm that the African Sacred Ibis is a generalist feeder and therefore, ecological impacts of its feeding strategies particularly on invasive snails should be further investigated.

Keywords:    African Sacred Ibis; feeding; diet; molluscs; generalist;