A less obvious but very real danger is predation of the chicks by other bird species or mammals such as mongooses. The tying back or cutting away of vegetation, known as 'gardening', in order to get a clear view into the nest used to be an accepted practise but is very much frowned upon these days. The risk is particularly great here in Africa where there are so many opportunistic species looking for a tasty snack of nestlings. I believe that under no circumstances should a nest be 'gardened' - rather look for another that does allow a clear view for photography. On occasions I have checked out a dozen or more nests of the same species before finding one suitable for photography without the need for tampering.
Hides are, of course, essential for nest photography.
It is important to habituate the birds to the hide by first erecting the hide some distance from the nest and then gradually moving it closer over a period of days. After each move, watch the hide from a distance with binoculars to check that the parents return confidently to the nest. If the birds show any signs of nervousness or unease, pack up the hide and leave them in peace. The final move of the hide into a position for photography should only be attempted after the chicks have hatched as the parental tie will be stronger. Also use your longest lens so that the hide can be kept as far away from the nest as possible.