This was seen in March, this year at Selinda, Botswana.
Like other hornbills, to protect its nest, the female seals itself in a tree hollow. It leaves a fissure. The male feeds them, female and chicks, through it.
In this case, the nest is close to the ground, at the level of the top of the crow feet, so at all predator’s mercy. The danger for the nest to be plundered is great.