Why does the Torah use the expression "Ki Yikarei Kan Tzipor ... "
Rashi: To confine the Mitzvah of Shilu'ach ha'Kein to where one comes across the nest by chance - to preclude a nest that one prepared. 1
See also Ba'al ha'Turim.
What does "Lo Sikach ha'Eim al ha'Banim"?
Rashi: It means 'Don't take the mother whilst she is still (crouching) on the babies. 1
See Sifsei Chachamim.
Why does the Torah insert the word "ba'Derech"?
Torah Temimah (citing Chulin, 139b): Like a road where the nest is not in your hand, to preclude birds that have made their nests inside your house and Herodian pigeons, 1 which are 'in your hand' and are therefore not subject to Shilu'ach ha'Kein.
Which roam among the people - See Sifsei Chachamim.
Why does the Torah add the words "O al ha'Aretz"?
Torah Temimah (citing the Sifri): To include a nest that is inside a pit, a trench or a cave.
What are the implications of "Rovetzes"?
Torah Temimah (citing Chulin, 140b): It precludes where the mother is hovering above the fledglings or the eggs, but includes where its wings are touching the nest.
What are the implications of "Efrochim O Beitzim"?
What is the underlying reason behind the Mitzvah of Shilu'ach ha'Kein?
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. 3
Rashbam: It is a form of cruelty and to take a mother and her babies and Shecht, cook and eat them together. 4
See Ramban DH 've'Kasav ha'Rav'.