Perching birds (the passerines) - birds of prey, parrots and all those delightful small wrens, warblers, finches and so on - are very sensitive around their nesting areas and may desert their chicks if disturbed. I concentrate on their many other fascinating behaviours and keep away from nests. If your objective is photographing nesting birds, learn as much as you can of the birds' behaviour and work from a hide.