Chulin3: 4
וְאֵלּוּ כְּשֵׁרוֹת בָּעוֹף: נִקְּבָה הַגַּרְגֶּרֶת אוֹ שֶׁנִּסְדְּקָה, הִכַּתָּה חֻלְדָּה עַל־רֹאשָׁהּ מְקוֹם שֶׁאֵינוֹ עוֹשֶׂה אוֹתָהּ טְרֵפָה, נִקַּב הַזֶּפֶק — רַבִּי אוֹמֵר: אֲפִלּוּ נִטַּל; יָצְאוּ בְנֵי מֵעֶיהָ וְלֹא נִקְּבוּ, נִשְׁתַּבְּרוּ גַפֶּיהָ, נִשְׁתַּבְּרוּ רַגְלֶיהָ, נִמְרְטוּ כְנָפֶיהָ. רַבִּי יְהוּדָה אוֹמֵר: אִם נִטְּלָה הַנּוֹצָה, פְּסוּלָה.
And the following are kosher in fowl: [If] the trachea was punctured or slit, [if] a weasel struck it on its head in a place where it does not render it treifah, [if] the crop was punctured — Rabbi says: Even if it was removed; [if] its intestines came out and were not punctured, [if] its wings were broken, [if] its legs were broken, or [if] its feathers were plucked. R’ Yehudah says: [If] the down was removed, it is unfit.