Of bills and beaks
Each bird species has a beak adapted to its particular function. Whether on hornbill or waxbill - the long or the short - they can be called beaks or bills. The bill is the hard, growing cuticle, similar to nails and claws, in front of the 'nose' (cere) to the tip. The outer layer of the bill continues to grow during the life of the bird. If not worn down by normal use, beaks can become overgrown, as with human finger nails.
This is often seen in captive birds that are fed soft foods where there is no natural wear on the beak. The same applies to claws and hooves and horns on mammals. This overgrowth often requires gentle 'coping' to regain the natural shape, which is maintained by normal daily wear.
In species with long beaks - and regardless of tip-wear - there is a continuous lengthening of the beak during the lifetime of the individual. As with horns in many ungulates, this becomes a useful criteria for the ageing of hornbills, storks and other species. One duck was recorded at 45 years old, while some parrots and eagles can live double that age. Normally the larger species live longer. Next time you see a yellow-billed hornbill try and estimate how long it has been around - probably not more than 15 years.