Rashi and Rashbam: To confine the Mitzvah of Shilu'ach ha'Ken to where one comes across the nest by chance - to preclude Mezuman ¹ (a nest that has been designated). ²

Chulin 139b & 140b: To teach us that the Mitzvah of Shilu'ach ha'Ken is confined to where one comes across the nest, and that one is not obligated to go and search for one in order to fulfil the Mitzvah, ³

Chulin 140b: "Kan" implies that one is Chayav to send away the mother even for one chick or one egg. ¹

Targum Yonasan and Chulin 139b: It implies a Tahor species of bird. ¹

Chulin, 139b: To teach us that the obligation to send away the mother bird applies even to a nest which belonged to you but where the birds rebelled (and no longer allowed to come close). ¹

Chulin, 139b: "Lefanecha", implies that the nest is in the R'shus ha'Yachid, ² "ba'Derech", that it is in the R'shus ha'Rabim.

Chulin, 139b #1: "Lefanecha" refers to a R'shus ha'Yachid; "ba'Derech" refers to a R'shus ha'Rabim, and precludes birds that have made their nests inside your house and Herodian pigeons ¹ which are 'in your hand'. ²

Chulin 139b #2: "Lefanacha" includes birds that were owned and fled; "ba'Derech" includes a nest on the sea - "ba'Yam Darech."

Rashi: It means that one may not take the mother whilst she is still (crouching) on the babies [or eggs]. ¹

Chulin, 139b #1: "Lefanecha" refers to a Reshus ha'Yachid. "Ba'Derech" refers to a Reshus ha'Rabim, and precludes birds that have made their nests inside your house and Herodian pigeons. ¹ which are 'in your hand..' ²

Chulin 139b #2: "Lefanacha" includes birds that were owned and fled. "Ba'Derech" includes a nest on the sea - "ba'Yam Darech."

Chulin 139b: To include a nest that is inside a pit, a trench or a cave.

Chulin, 140b: It precludes where the mother is hovering above the fledglings or the eggs, but includes where its wings are touching the nest.

Chulin, 140b: To compare the eggs to the fledglings, in that they can live, ¹ and the fledglings to the eggs, in that, like the eggs, they are not (yet) able to fly. ²

Ramban #1, Rashbam and Targum Yonasan: Refer to Vayikra, 22:28:3:1. ¹

Ramban #2: The same reasons apply here and to the Mitzvah of "Oso ve'Es B'no Lo Sishchatu be'Yom Echad." Refer to Vayikra, 22:28:3:2.

Ramban #3 (citing Moreh Nevuchim): Because the feelings of a mother towards her children are the same in an animal as in humans, and it is therefore particularly cruel to kill a baby animal in front of its mother. ²

Rashbam: Because it is cruel. ³

Oznayim la'Torah #1: Because, due to the fact that, as opposed to other species of animals, it lays eggs - which rely on the mother for a long time until they hatch and then, again, until the fledglings are ready to fend for themselves, the love between the mother and the babies is exceptionally strong and it would be cruel to take the babies from in front of the mother. ⁴

Oznayim la'Torah #2: The Torah forbids to take the mother, not the eggs or the fledglings, so as not to exploit the bird's love for its babies (See answer #5) - seeing as it is only due to that love that it did not fly away when the person approached the nest, but remained to defend its babies with its life if necessary. ⁵

Chulin 140b (according to the Chachamim) and Sifri: He is exempt from the Mitzvah of Shilu'ach ha'Ken, even if it is a male Korei (partridge), which normally sits on the eggs. ¹