“The hornbills are famous for their habit of immuring their nest. Before mating, the male offers the female a food gift (an insect or a fruit). The nest is usually made in a tree hole. Manipulating her bill like a trowel, the female uses clay and her own dejections to wall the entrance into the nest, inside of which she remains a prisoner. The male consolidates this “prison” on the exterior. This way, the nesting female is protected against monkeys, squirrels, martins or snakes. The female and the chicks are fed by the male with fruits, lizards, insects and frogs up to 10 times per hour. The male can bring up to 60 fruits at once, that he later regurgitates for the female. During the whole period of nesting, the male can bring up to 24,000 fruits for the female.
In order to not impede the growth of the chicks, the female inside the nest keeps her tail raised. When the chicks are well developed (at 6-7 weeks after hatching), the female breaks the entrance and starts helping the male in feeding the young. The entrance is walled back and will continue to remain so for the following 45-86 days, as long as caring for the chicks lasts.
The male molts successively, being always able to fly, while the female molts completely, while closed inside the nest. Large hornbills live up to 30 years.
The male communicates with the females found inside the nest via the noise made by their beating wing. The noise resembles the hiss of a steam engine, due to a special structure of the plumage that allows the sudden entrance of the air.” [source] 🍃