2,611. A Bird on One Egg
Hilchos Shechita 13:16
If the mother bird is standing on two branches with the nest in between them, we calculate. If removing the branches would make the mother fall onto the nest, one must send her away.
Hilchos Shechita 13:17
If the mother bird is on one chick or one egg, one must send her away. If a person finds a nest floating on the water or on the back of an animal, he must send the mother away. The Torah specifies “chicks or eggs” (in the plural) and “in a tree or on the ground” only because the Torah discusses the normal order of things.