2/4 Half of the Oriental pied hornbills stayed at stage 5 and the other half reached stage 6. Interestingly, those that did not reach level 6 also had no breeding experience, which may not be a coincidence. The hornbills certainly show a curious breeding behavior.

3/4 The female enters the hollow of a tree to lay her eggs, but first she covers the entrance from the inside with mud and saliva. An opening is left in the wall through which the male feeds the female and the young, without any visual contact.