By Rabbi Dovid Markel
The Torah states regarding an individual who desires to eat the eggs that the mother bird is incubating:
“If a bird’s nest chances before you on the road, on any tree, or on the ground, and [it contains] fledglings or eggs, if the mother is sitting upon the fledglings or upon the eggs, you shall not take the mother upon the young. You shall send away the mother, and [then] you may take the young for yourself, in order that it should be good for you, and you should lengthen your days.”
Maimonides explains that this commandment expresses the mercy that G-d has on all his creatures:
“The same reason applies to the law which enjoins that we should let the mother fly away when we take the young. The eggs over which the bird sits, and the young that are in need of their mother, are generally unfit for food, and when the mother is sent away, she does not see the taking of her young ones, and does not feel any pain…If the Law provides that such grief should not be caused to cattle or birds, how much more careful must we be that we should not cause grief to our fellowmen.”
Maimonides states “There is no difference in this case between the pain of man and the pain of other living beings, since the love and tenderness of the mother for her young ones is not produced by reasoning, but by imagination, and this faculty exists not only in man but in most living beings.”
The Torah mandates that just as we are to be concerned for the infliction of pain on a human being, so too must we be concerned for the nuisance that we may cause to an animal.