Halakhah zu Dewarim 22:7

He prohibited us - that we not take the nest at the time of the snare - the mother and the young. And that is His saying, "you shall not take the mother bird upon the young" (Deuteronomy 22:6). And this negative commandment is rectified by a positive commandment; and that is, "You must surely send away the mother, and you may take the young for yourself" (Deuteronomy 22:7). And anytime it is [no longer] possible to send [it] away and to fulfill the positive commandment in it - such as when the mother died before he sent it away - he is lashed. And the regulations of this commandment have already been explained at the end of Chullin. (See Parashat Ki Teitzeh; Mishneh Torah, Ritual Slaughter 13.)

To send away the mother [bird] if he takes it upon the young: To send away the mother from the nest before he takes the young, as it is stated (Deuteronomy 22:7), "you shall surely send away the mother and the young you shall take for you."

From the laws of the commandment is that which they, may their memory be blessed, said (Chullin 139b), "'If you chance upon a bird's nest in front of you on the path' - just like the path which is not acquired by you; so too all, etc. From here they said, 'Doves from the coop and doves from the attic that nested in cubicles and in edifices, and geese and chickens that nested in an orchard, [one is] obligated in sending away; but [if] they nested within the house, and also Herodian doves, [one is] exempt from sending away. [... And] Rav Yehudah ... said, '[If] he found a nest in the sea, [he is] obligated in sending away,'" as it is included in the expression, 'on the path,' "as it states (Isaiah 43:16), 'So said the Lord, who makes a path in the sea.'" And (Chullin 12:3) "[If] it was flying - [... if] its wings do not touch the nest, one is exempt from sending. [... If] there were [...] damaged eggs, one is exempt from sending, as it states (Deuteronomy 22:6), '[...] young birds or the eggs' - just as young birds are viable, so too [the] eggs [must be] viable [to fall under the law...]. If one sent her away and she returned, [...] - even [several] times - one is obligated [to send her away again], as it states (Deuteronomy 22:7),' You shall surely send.'" And the rest of the details of the commandment are elucidated in the last chapter of Chullin.