The northern red-billed hornbill (Tockus erythrorhynchus) is a species of hornbill in the family Bucerotidae. It is found from southern Mauritania through Somalia and northeast Tanzania. There are five species of red-billed hornbills recognized, but all five were once considered conspecific and some authorities still classify the others as subspecies of Tockus erythrorhynchus. During incubation, the female lays three to six white eggs in a tree hole, which is blocked off with a plaster of mud, droppings and fruit pulp. There is only one narrow aperture, just big enough for the male to transfer food to the mother and the chicks. When the chicks and the female are too big for the nest, the mother breaks out and rebuilds the wall. Then both parents feed the The female red-billed hornbill protects her young against intruders by building a wall across the opening of her nest. She then seals herself in and brings up her chicks in a 'prison'.They are omnivorous, taking insects, fruit and seeds. They feed mainly on the ground and will form flocks outside the breeding season chicks.
Source : Wikipedia