A wading bird with long legs and a long, down-curved bill with which it probes in mud for small invertebrates, especially crustaceans. Ibis usually feed in groups and most species nest in trees. There are 28 species (family Threskiornithidae), found worldwide. The white and black sacred ibis (Threskionis aethiopicus) of sub-Saharan Africa was venerated in ancient Egypt as a symbol of the god Thoth.