Halacha
הלכה א
הַלוֹקֵחַ אֵם עַל הַבָּנִים וּשִׁחָטָהּ. הַבָּשָׂר מֻתָּר בַּאֲכִילָה וְלוֹקֶה עַל שְׁחִיטַת הָאֵם שֶׁנֶּאֱמַר (דברים כב ו) "לֹא תִקַּח הָאֵם עַל הַבָּנִים". וְכֵן אִם מֵתָה קֹדֶם שֶׁיְּשַׁלְּחֶנָּה לוֹקֶה. וְאִם שִׁלְּחָהּ אַחַר שֶׁלְּקָחָהּ פָּטוּר:
כסף משנה
1.
When a person takes a mother together with its young and slaughters it, the meat is permitted to be eaten.1The fact that he violated a transgression in taking the mother does not cause the meat to be prohibited. He is, however, liable for lashes for slaughtering the mother,2Sefer HaMitzvot (negative commandment 306) and Sefer HaChinuch (mitzvah 544) include this prohibition among the 613 mitzvot of the Torah.The person transgresses the prohibition when he takes the mother and the offspring. Nevertheless, as long as the mother is alive and he can correct his deed by sending her away, he is not liable for lashes. This follows the principle of lav hanitak li'asai, a prohibition that can be corrected by a positive commandment, as stated in the following halachah. as [Deuteronomy 22:6] states: "Do not take the mother together with its offspring." Similarly, if it died before he sent it away, he is liable for lashes.3For he can no longer fulfill the positive commandment. If he sent it away after he took it, he is not liable.4For he corrected his actions through the positive commandment. Nevertheless, at the outset, it is forbidden for him to take the mother. He must send it away first, as is the simple meaning of the Torah's commandment. See Siftei Cohen 292:11.
הלכה ב
וְכֵן כָּל מִצְוַת לֹא תַּעֲשֶׂה שֶׁנִּתְּקָה לַעֲשֵׂה חַיָּב לְקַיֵּם עֲשֵׂה שֶׁבָּהּ. וְאִם לֹא קִיְּמוֹ לוֹקֶה:
כסף משנה
2.
Similarly, [with regard to] all negative commandments that can be corrected by a positive commandment,5The positive commandment to send away the mother bird is also considered as one of the 613 mitzvot of the Torah [Sefer HaMitzvot (positive commandment 148); Sefer HaChinuch (mitzvah 545)].See the Kessef Mishneh (to Halachah 19) which explains that Chullin 141a mentions a difference of opinion concerning this mitzvah between Rabbi Yehudah and the Sages. Rabbi Yehudah maintains - and this is the simple meaning of the verse - that the positive commandment requires one to send away the mother bird only before taking it. Thus according to his view, sending away the mother after it was taken does not fulfill a mitzvah and hence, does not correct the transgression. The Sages differ and maintain that the halachic definition of the mitzvah also includes sending away the bird after it was taken. Therefore, if one took the mother together with its young, he can correct his transgression by sending away the mother. The Rambam's decision reflects the Sages' position. one is obligated to fulfill the positive commandment. If he does not fulfill it, he is liable for lashes.6See Makkot 16b which mentions a difference of opinion concerning the matter. One view maintains that as long as the person does not prevent himself from correcting the transgression through his own conduct, e.g., with regard to the matter at hand, he did not kill the mother bird, he is not lible for lashes. The other view, which as above is accepted as halachah by the Rambam, is that the person becomes liable for lashes when he violates the transgression. It is just that the punishment is suspended as long as he has the opportunity to correct the matter. Once, however, that opportunity no longer exists, even if it is not his fault - e.g., in the matter at hand, the bird dies - that punishment is meted out.
הלכה ג
בָּא אֶחָד וְחָטַף הָאֵם מִיָּדוֹ וְשִׁלְּחָהּ אוֹ שֶׁבָּרְחָה מִתַּחַת יָדוֹ שֶׁלֹּא מִדַּעְתּוֹ לוֹקֶה שֶׁנֶּאֱמַר (דברים כב ז) "שַׁלֵּחַ תְּשַׁלַּח" עַד שֶׁיְּשַׁלֵּחַ מֵעַצְמוֹ וַהֲרֵי לֹא קִיֵּם עֲשֵׂה שֶׁבָּהּ:
כסף משנה
3.
If another person comes and seizes the mother bird from his hands and sends it away or it took flight from his possession without his knowledge, he is liable for lashes. [This is implied by ibid.:7]: "You shall certainly send away [the mother]," i.e., he must send away [the mother bird] himself. [If not,] he did not fulfill the related positive commandment.7And is therefore held liable for the violation of the negative commandment.הלכה ד
נָטַל אֵם עַל הַבָּנִים וְקִצֵּץ אֲגַפֶּיהָ כְּדֵי שֶׁלֹּא תָּעוּף וְשִׁלְּחָהּ מַכִּין אוֹתוֹ מַכַּת מַרְדּוּת. וּמַשְׁהֶה אוֹתָהּ אֶצְלוֹ עַד שֶׁיִּגְדְּלוּ כְּנָפֶיהָ וּמְשַׁלְּחָהּ. וְאִם מֵתָה קֹדֶם לָזֶה אוֹ בָּרְחָה וְאָבְדָה לוֹקֶה שֶׁהֲרֵי לֹא קִיֵּם עֲשֵׂה שֶׁבָּהּ:
כסף משנה
4.
If he took a mother bird together with its young, cut off its wings so that it cannot fly and sent it away,8I.e., he is trying to perform the mitzvah by sending the mother bird away on its feet so that he will not be held liable and yet will be able to take it again shortly afterwards. See Shulchan Aruch (Yoreh De'ah 292:4). he is given stripes for rebellious conduct.9I.e., he is punished for his defiance of the spirit of the Torah's commandments even though it is possible that he will not actually be held liable for lashes. [He must] keep [the mother bird] in his possession until her wings grow back and then send her away. If [the mother] died before this or fled and was lost, he is liable for lashes, for he did not fulfill the related positive commandment.הלכה ה
וְכֵיצַד מְשַׁלֵּחַ הָאֵם. אוֹחֵז בִּכְנָפֶיהָ וּמַפְרִיחָהּ. שִׁלְּחָהּ וְחָזְרָה וְשִׁלְּחָהּ וְחָזְרָה אֲפִלּוּ אַרְבַּע וְחָמֵשׁ פְּעָמִים חַיָּב לְשַׁלֵּחַ שֶׁנֶּאֱמַר (דברים כב ז) "שַׁלֵּחַ תְּשַׁלַּח":
כסף משנה
5.
How must one send away the mother? He holds her by her wings and has her fly away. If he sent her away and she returned, he sent her away and she returned10I.e., as long as the mother returns before he takes the young so that the mitzvah is still relevant (Siftei Cohen 292:8). - even if this happens - four or five times, he is obligated to send her away, as [implied by the repetition of the verb in the] phrase: "You shall certainly send away."11See Bava Metzia 31a which gives several examples of how the repetition of a verb in the Torah implies that a commandment must be fulfilled even 100 times.הלכה ו
הָאוֹמֵר הֲרֵינִי נוֹטֵל אֶת הָאֵם וּמְשַׁלֵּחַ אֶת הַבָּנִים חַיָּב לְשַׁלֵּחַ אֶת הָאֵם שֶׁנֶּאֱמַר (דברים כב ז) "שַׁלֵּחַ תְּשַׁלַּח אֶת הָאֵם":
כסף משנה
6.
Although a person says "I will take the mother bird and send away the young,"12And thus seemingly, he will be fulfilling the intent of the Torah's commandment, for he will not be taking the mother and the young together. he is obligated to send away the mother bird, as the verse states: "You shall certainly send away the mother."הלכה ז
לָקַח אֶת הַבָּנִים וְהֶחֱזִירָן לַקֵּן וְאַחַר כָּךְ חָזְרָה הָאֵם עֲלֵיהֶן פָּטוּר מִלְּשַׁלֵּחַ. שִׁלֵּחַ אֶת הָאֵם וְחָזַר וְצָד אוֹתָהּ הֲרֵי זֶה מֻתָּר. לֹא אָסְרָה תּוֹרָה אֶלָּא לָצוּד אוֹתָהּ וְהִיא אֵינָהּ יְכוֹלָה לִפְרֹחַ בִּשְׁבִיל הַבָּנִים שֶׁהִיא מְרַחֶפֶת עֲלֵיהֶן שֶׁלֹּא יִלָּקְחוּ שֶׁנֶּאֱמַר (דברים כב ו) "וְהָאֵם רֹבֶצֶת עַל הָאֶפְרֹחִים". אֲבָל אִם הוֹצִיאָהּ מִתַּחַת יָדוֹ וְחָזַר וְצָד אוֹתָהּ מֻתָּר:
כסף משנה
7.
If he [sent away the mother,]13This addition is made on the basis of Shulchan Aruch (Yoreh De'ah 292:5). took the offspring and [then] returned them to the nest and the mother came back to them, he is not obligated to send [her] away.14Once he has taken the offspring, they are considered as "at hand," and this mitzvah no longer applies as stated in the following halachah and notes (Siftei Cohen 292:10).It is permitted to send away the mother and then snare her again. The Torah forbade snaring only when she cannot fly away because of her offspring over which she is hovering so that they not be taken,15For, as emphasized in Moreh Nevuchim, Vol. III, ch. 48, which explains that this is the motivating rationale for this mitzvah: to prevent the cruel act of taking the young in front of the mother. Note, however, Hilchot Tefilah 9:7 and the resolution of the apparent contradiction in the previous chapter. as [ibid.:6] states: "And the mother is resting on the chicks." If, however, he removed her from his grasp and then snared her again, it is permitted.
הלכה ח
שִׁלּוּחַ הָאֵם אֵינוֹ נוֹהֵג אֶלָּא בְּעוֹף טָהוֹר שֶׁאֵינוֹ מְזֻמָּן כְּגוֹן יוֹנֵי שׁוֹבָךְ וַעֲלִיָּה וְעוֹפוֹת שֶׁקִּנְּנוּ בַּפַּרְדֵּס שֶׁנֶּאֱמַר (דברים כב ו) "כִּי יִקָּרֵא". אֲבָל הַמְזֻמָּן כְּגוֹן אֲוָזִין וְתַרְנְגוֹלִין וְיוֹנִים שֶׁקִּנְּנוּ בַּבַּיִת אֵינוֹ חַיָּב לְשַׁלֵּחַ:
כסף משנה
8.
[The mitzvah to] send away the mother bird applies only with regard to a kosher species of fowl16Chullin 139b derives this concept from the exegesis of the prooftext from Deuteronomy. that are not at hand, e.g., doves that rested in a dovecote or on a loft,17When quoting this law, the Shulchan Aruch (Yoreh De'ah 292:2 and commentaries) emphasizes that if the nest is within the person's property and the mother bird lifts itself up, the person automatically acquires the offspring. From that time on, they are considered as "at hand" and the mitzvah does not apply. See Halachah 18 and notes. wild fowl that nested in an orchard. [This is derived from the phrase (ibid.)]: "When you will chance upon." When, however, [fowl is] at hand, e.g., ducks, chicken, and doves that nested in a building, one is not liable to send away the mother.הלכה ט
הָיוּ הָאֶפְרוֹחִין מַפְרִיחִין שֶׁאֵינָן צְרִיכִין לְאִמָּן אוֹ בֵּיצִים מוּזָרוֹת אֵינוֹ חַיָּב לְשַׁלֵּחַ. הָיוּ אֶפְרוֹחִין טְרֵפוֹת הֲרֵי אֵלּוּ כְּבֵיצִים מוּזָרוֹת וּפָטוּר מִלְּשַׁלֵּחַ:
כסף משנה
9.
If the chicks could fly and thus they no longer needed their mother or [the mother was sitting on] unfertilized eggs,18Our translation is based on Rashi's commentary to Chullin 64b. he is not obligated to send away [the mother]. If the chicks were trefot, it is comparable to unfertilized eggs and he is not liable to send away [the mother].19Chullin, loc. cit., notes that the verse mentions both eggs and chicks and derives both of these concepts from an equation it establishes between the two: Just as the chicks are entities that will continue to exist, so too, the eggs must be entities that will continue to exist [in contrast to unfertilized eggs that will spoil after a certain time]. Just as the eggs require their mother, so too, the chicks must require their mother.הלכה י
זָכָר שֶׁמְּצָאוֹ רוֹבֵץ עַל הַקֵּן פָּטוּר מִלְּשַׁלֵּחַ. עוֹף טָמֵא רוֹבֵץ עַל בֵּיצֵי עוֹף טָהוֹר אוֹ עוֹף טָהוֹר רוֹבֵץ עַל בֵּיצֵי עוֹף טָמֵא פָּטוּר מִלְּשַׁלֵּחַ:
כסף משנה
10.
When a male fowl is resting on a nest, one is not obligated to send him away [before taking the young].20Chullin 140a emphasizes that the verse mentions a mother, implying "and not a father." When a non-kosher bird is resting on the nest of the eggs of a kosher fowl or a kosher fowl is resting on the eggs of a non-kosher fowl, one is not obligated to send away [the fowl that is resting].21For Chullin 138b states that the verse forbids taking the bird and its offspring "for yourself." Implied is that there is no prohibition when taking it for your dogs, i.e., taking a non-kosher species which is fit only to be fed to the dogs.הלכה יא
הָיְתָה רוֹבֶצֶת עַל בֵּיצִים שֶׁאֵינָן מִינָהּ וְהֵן טְהוֹרִין הֲרֵי זֶה מְשַׁלֵּחַ. וְאִם לֹא שִׁלֵּחַ אֵינוֹ לוֹקֶה. הָיְתָה הָאֵם טְרֵפָה חַיָּב לְשַׁלְּחָהּ:
כסף משנה
11.
When a [kosher fowl] was resting on kosher eggs of a different species, one should send [the bird] away. If, however, one fails to do so, one is not liable.22There is an unresolved question concerning this issue in Chullin 140b. Hence, it is forbidden to take the birds, but one is not liable for lashes because of the doubt. If the mother is trefe, he is obligated to send her away.23Even though it is forbidden to eat the mother, there is a difference between it and a fowl from a non-kosher species. A mother from a non-kosher species is excluded because the prooftext uses the term tzipor which indicates a kosher species. A bird which is trefe, though forbidden, is still a tzipor (Siftei Cohen 292:1).הלכה יב
שָׁחַט מִקְצָת סִימָנִין בְּתוֹךְ הַקֵּן קֹדֶם שֶׁיִּקָּחֶנָּה חַיָּב לְשַׁלֵּחַ וְאִם לֹא שִׁלֵּחַ אֵינוֹ לוֹקֶה:
כסף משנה
12.
When one slits a portion of the gullet24The literal meaning of the Rambam's words is "If he cut a portion of the signs." We have translated the Rambam's words as above because as obvious from the conclusion of his ruling, there is a doubt whether he is obligated to send away the mother bird. And with regard to the windpipe there is no doubt that he is obligated to send away the mother.To explain: Chullin 140b questions: "Do we say that since after slitting a portion of the signs the animal will be trefe, is there a need to send it away?" Now, if a person slits less than half the windpipe, the fowl is not trefe and if he slits more than half of it, its slaughter is completed. Hence, we are forced to say that he is speaking about cutting a portion - but less than half - of the gullet. If he does not complete the slaughter, making such a slit will render the fowl trefe. [of the mother]25The fact the Rambam uses the term sheyikachenah, "before he takes her," implies that he is speaking about the mother bird. This understanding is also acknowledged by the Tur and Rabbenu Nissim. In his Kessef Mishneh, Rav Yosef Caro questions that interpretation, noting that even if the mother bird was made trefe by slitting its gullet, it would have to be sent away as stated in the previous halachah. Therefore, he suggests amending the text of the Mishneh Torah to imply that the signs of the chicks were slit and the question is, since he is involved in the slaughter of the chicks and stopping to send away the mother would render them trefe, must he stop and send her away or not. He follows this interpretation in his Shulchan Aruch (Yoreh De'ah 292:10). before he took her, he is liable to send her away. If he did not send her away, he is not liable for lashes.26Since the Talmud does not resolve the question it raises, one cannot be held liable for lashes because of the doubt.
הלכה יג
הָיְתָה מְעוֹפֶפֶת. אִם כְּנָפֶיהָ נוֹגְעוֹת בַּקֵּן חַיָּב לְשַׁלֵּחַ. וְאִם לָאו פָּטוּר מִלְּשַׁלֵּחַ. הָיְתָה מַטְלִית אוֹ כְּנָפַיִם חוֹצְצוֹת בֵּין כְּנָפֶיהָ וּבֵין הַקֵּן הֲרֵי זֶה מְשַׁלֵּחַ. וְאִם לֹא שִׁלֵּחַ אֵינוֹ לוֹקֶה:
כסף משנה
13.
[The following laws apply if the mother bird] was hovering [over the nest]: If her wings were touching the nest, one is obligated to send her away.27The Torah uses the expression "resting on the nest." Chullin 40b infers that if the mother is hovering over the nest, the mitzvah does not imply. Since the verse does not use the term "sitting," however, we learn that the obligation exists even when the mother is not sitting in the nest but lingering close by in a manner that its wings are touching. If not, he is not obligated. If there was a cloth or feathers intervening between her wings and the nest, he must send her away. If he did not send her away, he is not liable for lashes.28This question is left unresolved by Chullin, loc. cit. Hence, the Rambam rules that one must be stringent and send away the mother, but because of the doubt, cannot be held liable for lashes if he did not.הלכה יד
הָיוּ שְׁנֵי סִדְרֵי בֵּיצִים וּכְנָפֶיהָ נוֹגְעוֹת בַּסֵּדֶר הָעֶלְיוֹן. אוֹ שֶׁהָיְתָה רוֹבֶצֶת עַל בֵּיצִים מוּזָרוֹת וְתַחְתֵּיהֶן בֵּיצִים יָפוֹת. אוֹ שֶׁהָיְתָה אֵם עַל גַּבֵּי אֵם. אוֹ שֶׁהָיָה הַזָּכָר עַל הַקֵּן וְהָאֵם עַל הַזָּכָר. הֲרֵי זֶה לֹא יִקַּח. וְאִם לָקַח יְשַׁלֵּחַ וְאִם לֹא שִׁלֵּחַ אֵינוֹ לוֹקֶה:
כסף משנה
14.
If there were two rows of eggs and [the mother bird's] wings were touching [only] the top row, [the mother bird] was sitting on unfertilized eggs, but there were good eggs below them, one female was sitting on another female, a male was sitting on the nest and the female was sitting on the male - [in all these situations,] one should not take [the mother bird with the offspring]. If he takes [her], he should send her away. But if he does not send her away, he is not liable for lashes.29All of these situations are questions left unresolved by Chullin 140b. Hence, as above, one must be stringent and send away the mother, but because of the doubt, cannot be held liable for lashes if he did not.הלכה טו
הָיְתָה יוֹשֶׁבֶת בֵּין הָאֶפְרוֹחִים אוֹ בֵּין הַבֵּיצִים וְאֵינָהּ נוֹגַעַת בָּהֶן פָּטוּר מִלְּשַׁלֵּחַ. וְכֵן אִם הָיְתָה בְּצַד הַקֵּן וּכְנָפֶיהָ נוֹגְעוֹת בַּקֵּן מִצִּדּוֹ פָּטוּר מִלְּשַׁלֵּחַ:
כסף משנה
15.
If [the mother bird] was sitting among the young or the eggs and was not touching them,30In his Kessef Mishneh, Rav Yosef Caro mentions a question raised by Rabbenu Nissim: Since touching the nest from the side is not sufficient as indicated by the concluding clause in the halachah, what does it matter if the mother bird touches its young from the side when it sits among them? Based on that objection, in his Shulchan Aruch (Yoreh De'ah 292:12), he incorporates Rabbenu Nissim's understanding when quoting this law. one is not liable to send her away.31For the Torah speaks about the mother "resting on the eggs or the chicks" and not sitting at their side. Similarly, if she was at the side of the nest and her wings were touching the nest from the side, he is not obligated to send her away.הלכה טז
הָיְתָה עַל שְׁנֵי בַּדֵּי אִילָן וְהַקֵּן בֵּינֵיהֶן רוֹאִין כָּל שֶׁאִלּוּ יִנָּטְלוּ הַבַּדִּין תִּפּל עַל הַקֵּן חַיָּב לְשַׁלֵּחַ:
כסף משנה
16.
When [the mother bird was perched] on two branches of a tree and the nest was positioned between them, we make an evaluation. In all instances where the mother would fall on the nest if the branches were removed, one is obligated to send her away.32Rashi, Chullin 140b, states that this applies even if the mother's wings are not touching the nest. As long as she is resting directly above the nest, it is considered as if she was resting on it. The Siftei Cohen 292:17 quotes this point as halachah.הלכה יז
הָיְתָה רוֹבֶצֶת עַל אֶפְרוֹחַ אֶחָד אוֹ עַל בֵּיצָה אַחַת חַיָּב לְשַׁלֵּחַ. הַמּוֹצֵא קֵן עַל פְּנֵי הַמַּיִם אוֹ עַל גַּבֵּי בַּעֲלֵי חַיִּים חַיָּב לְשַׁלֵּחַ. לֹא נֶאֱמַר (דברים כב ו) "אֶפְרוֹחִים אוֹ בֵּיצִים" וְלֹא נֶאֱמַר (דברים כב ו) "בְּכָל עֵץ אוֹ עַל הָאָרֶץ" אֶלָּא שֶׁדִּבֵּר הַכָּתוּב בְּהוֹוֶה:
כסף משנה
17.
When the mother is resting on one chick or on one egg, one is obligated to send her away.33As evident from Chullin 12:3, the Biblical command speaks about "a nest." As long as a nest contains one egg or chick, it is still considered a nest. When a person finds a nest floating on the water or positioned on the back of an animal, he is obligated to send the mother away. [The verse] mentions "chicks or eggs"34Using a plural form. and "on any tree or on the ground" [not as exclusions], but because the Torah speaks about the commonplace situations.35This is a general principle applying with regard to many Biblical commandments. See Yevamot 15:2, Shabbat 65a, Nedarim 48a.הלכה יח
אָסוּר לִזְכּוֹת בַּבֵּיצִים כָּל זְמַן שֶׁהָאֵם רוֹבֶצֶת עֲלֵיהֶן. לְפִיכָךְ אֲפִלּוּ הָיְתָה רוֹבֶצֶת עַל הַבֵּיצִים אוֹ עַל הָאֶפְרוֹחִים בַּעֲלִיָּתוֹ וּשׁוֹבָכוֹ אֵינָן מְזֻמָּנִין. וְלֹא קָנָה לוֹ חֲצֵרוֹ. כְּשֵׁם שֶׁאֵינוֹ יָכוֹל לִזְכּוֹת בָּהֶן לַאֲחֵרִים כָּךְ לֹא תִּזְכֶּה לוֹ חֲצֵרוֹ בָּהֶן. וּלְפִיכָךְ חַיָּב לְשַׁלֵּחַ:
כסף משנה
18.
It is forbidden to acquire the eggs as long as the mother is resting upon them. Therefore even if a mother bird was resting on eggs or chicks in one's loft or dovecote, they are not considered as "at hand" and his courtyard does not acquire them for him.36The Rambam is referring to a principle in Jewish business law which maintains that a person can acquire property by virtue of its presence in his domain. As the Rambam states in Hilchot Gezelah Va'Avedah 17:8-11:A person's courtyard can acquire property for him without him being aware of it. Thus, if a lost object falls into a person's courtyard, he acquires it.
When does the above apply? When the courtyard is protected. [When, by contrast, a lost article enters a person's] field or garden [different rules apply]. If he is standing at the side of his field and says, "May my field acquire it for me," he acquires it. If, however, he is not standing there, or he is standing there but does not make such a statement [he does not acquire it.]...
The [potential for] a man [to acquire property by virtue of its presence in his] courtyard is derived, by contrast, from [the fact that] he is able to acquire an article via an agent. Just as an agent can acquire [an article] for him, so too, can he acquire [an article by virtue of its presence in his] courtyard....
[The following rules apply when a person] sees... young doves that cannot fly [in his property]: [When the following conditions are met:] he was standing at the side of his field, [the animals] were on his property, and he could catch them if he ran, he can acquire them [by virtue of their presence in] his field if he states: "May my field acquire them for me."
Thus in the case at hand, since the person cannot acquire the eggs himself until he sends away the mother, his courtyard cannot acquire them on his behalf (Chullin 141b).
Just as he cannot acquire them on behalf of others [until he sends away the mother], so, too, his courtyard cannot acquire them on his behalf.37For as stated in the quoted portion, the potential for a person's property to acquire an article on his behalf is derived from the laws of agency. Therefore, he must send [her] away.38As mentioned above, the Shulchan Aruch (Yoreh De'ah 292:2) states that if the mother bird lifted itself up, the person can acquire the chicks by virtue of their presence in his property even if he does not remove them from their nest. From that time on, they are considered as "at hand" and this mitzvah does not apply. Indeed, he can tap the nest so that the mother will rise up and then acquire the young (Kessef Mishneh).
הלכה יט
אָסוּר לִטּל אֵם עַל הַבָּנִים וַאֲפִלּוּ לְטַהֵר בָּהֶן אֶת הַמְצֹרָע שֶׁהִיא מִצְוָה. וְאִם לָקַח חַיָּב לְשַׁלֵּחַ. וְאִם לֹא שִׁלֵּחַ לוֹקֶה. שֶׁאֵין עֲשֵׂה דּוֹחֶה לֹא תַעֲשֶׂה וַעֲשֵׂה. (וַעֲשֵׂה) וְלֹא עֲשֵׂה דּוֹחֶה עֲשֵׂה:
כסף משנה
19.
It is forbidden to take a mother bird together with her offspring, even to purify a person with tzara'at.39A skin condition, resembling leprosy, that is visited upon a person as retribution for speaking gossip and slander. The purification process for such a person is described in Leviticus, ch. 14, and Hilchot Tuma'at Tzara'at 11:1. If he took [the mother], he is obligated to send her away. If he did not, he is liable for lashes.40As stated in Halachah 2. Even if he used the mother bird for a mitzvah, he still receives lashes for violating the transgression. [The rationale is that] a positive commandment41The purification of the person with tzara'at. does not supersede the observance of a negative commandment [that is reinforced] by a positive commandment.42The prohibition of taking the mother which is reinforced by the mitzvah to send her away. Note the Kessef Mishneh who questions whether the two mitzvot should be placed in this category, for according to the Sages (whose opinion is accepted as halachah), the two mitzvot do not apply at the same time. And a positive commandment does not supersede another positive commandment.43I.e., once he has taken the mother bird, he is obligated to send her away and the observance of another positive commandment, e.g., the purification rite mentioned above, does not supplant it.הלכה כ
הַמַּקְדִּישׁ עוֹף לְבֶדֶק הַבַּיִת וּפָרַח מִיָּדוֹ וַהֲרֵי הוּא מַכִּירוֹ וּמְצָאוֹ רוֹבֵץ עַל הָאֶפְרוֹחִים אוֹ עַל הַבֵּיצִים לוֹקֵחַ הַכּל וּמְבִיאָן לִידֵי גִּזְבָּר. שֶׁאֵין שִׁלּוּחַ הָאֵם נוֹהֵג בְּמֻקְדָּשִׁין שֶׁנֶּאֱמַר (דברים כב ז) "וְאֶת הַבָּנִים תִּקַּח לָךְ" וְאֵלּוּ אֵינָן שֶׁלְּךָ:
כסף משנה
20.
[The following rule applies when] a person consecrates a wild fowl to the Temple treasury, it flies away from his hand, but he recognizes it and finds it resting on chicks or on eggs. He should take the entire [nest]44For not only the mother, but also the offspring, belong to the Temple treasury. For the mother gave birth to them after she had been consecrated. and bring it to the Temple treasurer. [The rationale is that the mitzvah of] sending away the mother bird does not apply with regard to consecrated [fowl], as [implied by Deuteronomy 22:7]: "And you may take the offspring for yourself." These may not [be taken] for yourself.45For as above the offspring are also the property of the Temple treasury.Significantly, although the Rambam's ruling is based on Chullin 138b, he does not quote the wording of the Talmud, but instead, explains the derivation of the ruling in a different manner. The Lechem Mishneh explains that this reflects a pattern found frequently in the Mishneh Torah: The Rambam will explain the derivation of a law differently than the Talmud if it appears to him that his derivation is simpler and more direct.
הלכה כא
עוֹף שֶׁהָרַג אֶת הַנֶּפֶשׁ פָּטוּר מִלְּשַׁלֵּחַ מִפְּנֵי שֶׁהוּא מְצֻוֶּה לַהֲבִיאוֹ לְבֵית דִּין לָדוּן אוֹתוֹ:
כסף משנה