Reference for Chullin 12:3
הָיְתָה מְעוֹפֶפֶת, בִּזְמַן שֶׁכְּנָפֶיהָ נוֹגְעוֹת בַּקֵּן, חַיָּב לְשַׁלֵּחַ. אֵין כְּנָפֶיהָ נוֹגְעוֹת בַּקֵּן, פָּטוּר מִלְּשַׁלֵּחַ. אֵין שָׁם אֶלָּא אֶפְרוֹחַ אֶחָד אוֹ בֵיצָה אַחַת, חַיָּב לְשַׁלֵּחַ, שֶׁנֶּאֱמַר (דברים כב), קַן, קֵן מִכָּל מָקוֹם. הָיוּ שָׁם אֶפְרוֹחִין מַפְרִיחִין אוֹ בֵיצִים מוּזָרוֹת, פָּטוּר מִלְּשַׁלֵּחַ, שֶׁנֶּאֱמַר (שם), וְהָאֵם רֹבֶצֶת עַל הָאֶפְרֹחִים אוֹ עַל הַבֵּיצִים, מָה אֶפְרוֹחִין בְּנֵי קְיָמָא, אַף בֵּיצִים בְּנֵי קְיָמָא, יָצְאוּ מוּזָרוֹת. וּמָה הַבֵּיצִים צְרִיכִין לְאִמָּן, אַף הָאֶפְרוֹחִין צְרִיכִין לְאִמָּן, יָצְאוּ מַפְרִיחִין. שִׁלְּחָהּ וְחָזְרָה, שִׁלְּחָהּ וְחָזְרָה, אֲפִלּוּ אַרְבָּעָה וַחֲמִשָּׁה פְעָמִים, חַיָּב, שֶׁנֶּאֱמַר (שם), שַׁלֵּחַ תְּשַׁלַּח. אָמַר, הֲרֵינִי נוֹטֵל אֶת הָאֵם וּמְשַׁלֵּחַ אֶת הַבָּנִים, חַיָּב לְשַׁלֵּחַ, שֶׁנֶּאֱמַר (שם), שַׁלֵּחַ תְּשַׁלַּח אֶת הָאֵם. נָטַל הַבָּנִים וְהֶחֱזִירָן לַקֵּן וְאַחַר כָּךְ חָזְרָה הָאֵם עֲלֵיהֶם, פָּטוּר מִלְּשַׁלֵּחַ:
If the dam was fluttering about the nest, if she touched it with her wings, it is obligatory to let her fly away, but not when her wings do not touch it; if there was but one young bird, or one egg, it is nevertheless obligatory to let the dam fly away, because the Scripture uses the term (Deuteronomy 22:6): "nest," i.e. any nest. When some of the young birds are already on the wing, or that the eggs are addled, the precept does not apply, for it is written, "And the dam sitting upon the young birds, or upon the eggs." Even as the young birds are supposed in the text to be live ones, thus also must the eggs be fit for incubation [and to produce life], from which term addled eggs are [of course] excluded; and even as the eggs [to complete the process of incubation] require the care of the dam, thus also must the young bird mentioned in the text yet require the nurture of the dam, consequently those birds which are already able to fly are excluded. Should a person have let the dam fly away, and she returns constantly to the nest, even four or five times [or oftener], he is bound to let her fly away, for it is said, "Thou shalt surely let the dam go," &c. When a person says, "I take the dam, and set the young birds free," he must let the dam go also, since it is written, "Thou shalt surely let the dam go." If he takes the young birds first, and then puts them again in the nest, and the dam returns, he is no longer bound to let her fly away again.