The Sages derive from the verse, “If a bird’s nest happens to be before you,” that one need not search for a nest in order to fulfill this mitzva (Ḥullin 139b). A question nevertheless arises when someone does not want the chicks or eggs but comes across a bird’s nest: does he have a mitzva to send away the mother and take the chicks or eggs?
Many authorities maintain that the mitzva applies only when one actually wants the chicks or eggs; only then must he send away the mother before taking them. If he has no need for them, sending away the mother and taking the chicks is not a fulfillment of a mitzva. Accordingly, one should not do so since it causes needless animal suffering and destroys chicks or eggs for no reason.
Others maintain that whoever encounters a bird’s nest has a mitzva to send away the mother and take the young, even if he does not need them. Some kabbalists go further, maintaining that every Jew should seek out a bird’s nest in order to fulfill shilu’aḥ ha-ken at least once in his life. In their view, this does not violate bal tashḥit or tza’ar ba’alei ḥayim, since the act is done for the sake of a mitzva and therefore serves a human need.
In practice, the primary ruling follows the first view: if one does not want the chicks or eggs, he should not send away the mother, since doing so serves no mitzva purpose and involves tza’ar ba’alei ḥayim and bal tashḥit. One who nevertheless wishes to fulfill the mitzva according to the second view should drive the mother away without taking the chicks or eggs, either by shouting or by lightly tapping the nest. According to some authorities, once the mother has been driven away and the chicks or eggs are halakhically available to him, he has fulfilled the mitzva. This allows him to satisfy the second view without coming into conflict with the first (Ḥakham Tzvi §83; Shevet Yehuda YD 292; Or Sameaḥ, Laws of Yom Tov 3:8).[4]
[4]. The view that there is no mitzva to send away the mother when one has no need for the young is found in Rabbeinu Baḥya to Devarim 22:7 and Ran to Ḥullin 139a. This is also the position of Ha-Makneh to Kiddushin 41a; Ḥatam Sofer, OḤ §100; Netziv in Meromei Sadeh to Ḥullin 139b; and Maharam Schick on mitzva 545, and it seems to be the view of many other Rishonim and Aḥaronim as well.
Many Aḥaronim, however, maintain that one who finds a bird’s nest has a mitzva to send away the mother even if he has no need for the young. Ḥavot Ya’ir §67 inclines this way, and this is also the view of Birkei Yosef 292:8, AHS 292:1–2, and Maharsham 1:209. Arizal adds in Sha’ar ha-Gilgulim, Introduction 16, that every Jew must fulfill all the mitzvot he is able to fulfill. If he neglects even one mitzva, his soul must return to this world through reincarnation in order to complete it. If he failed to fulfill shilu’aḥ ha-ken only because no bird’s nest came his way, he is assured that when his soul returns, he will not sin in other ways. But if a bird’s nest did come his way and he failed to send away the mother, his soul must return again, with no such assurance. As explained above, one who is concerned for this view should follow the approach of Ḥakham Tzvi and drive away the mother without taking the chicks or eggs. This fulfills the mitzva according to the second view without coming into conflict with the first.
