Topic : Land Birds
Article 40 
05 November 2007
Crowned Hornbill breeding cycle – Part 1
Of the 3 hornbills that inhabit forest habitats in southern Africa, Crowned Hornbill Tockus alboterminatus is the smallest and the only predominantly insectivorous species. This series documents its breeding cycle with Part 1 illustrating the early nestling stage.
Male crowned Hornbill feeding well developed chicks in a nest
Nest
These hornbills require large enough tree cavities in which to raise 2 – 3 offspring and have enough room for the female to maneuver within the nest cavity. Nest entrance holes vary from narrow slits in tree trunks to natural round holes. The entrance hole is then partially sealed (leaving a narrow feeding slit).
Egg laying begins before the plastering process of the entrance tunnel has developed very far.
Incarceration and Moult
The female remains incarcerated in the nest for nearly two months, fed by the male. Soon after the female takes up residence in the cavity, and egg laying is complete, she undergoes an almost simultaneous moult of her flight and tail feathers. This is a critical stage in their breeding cycle because should something happen to the male, she could break out of the nest but because she is flightless, would, without a doubt, perish.
Her droppings, mixed with some nest debris are used to close up the nest entrance, leaving a narrow feeding slit.
Once her flight feathers have grown (about half way through the nestling period), she breaks out the nest and the chicks re-plaster the entrance tunnel. She then helps the male with the demanding job of satisfying the ever-hungry growing chicks.
Crowned Hornbill chicks during the early stages of growth
The female leaves the nest about half way through the nestling period and amazingly, the chicks re-plaster the entrance tunnel themselves.