The hornbills have a rather strange system of breeding. They breed in hollows in trees. The opening is mostly blocked off with a plaster made of mud and droppings, leaving only a narrow opening through which the male feeds the female and her chicks. When the hole becomes too small for its occupants, the female breaks out; the opening is then resealed as before, and the chicks fed by both parents until they are ready to leave the nest.
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