Reference for Zevachim 7:5
מָלַק בִּשְׂמֹאל, אוֹ בַלַּיְלָה, שָׁחַט חֻלִּין בִּפְנִים, וְקָדָשִׁים בַּחוּץ, אֵינָן מְטַמְּאִין בְּבֵית הַבְּלִיעָה. מָלַק בְּסַכִּין, מָלַק חֻלִּין בִּפְנִים, וְקָדָשִׁים בַּחוּץ, תּוֹרִין שֶׁלֹּא הִגִּיעַ זְמַנָּן, וּבְנֵי יוֹנָה שֶׁעָבַר זְמַנָּן, שֶׁיָּבַשׁ גַּפָּה, וְשֶׁנִּסְמֵת עֵינָהּ, וְשֶׁנִּקְטְעָה רַגְלָהּ, מְטַמֵּא בְבֵית הַבְּלִיעָה. זֶה הַכְּלָל, כֹּל שֶׁהָיָה פְסוּלָהּ בַּקֹּדֶשׁ, אֵינָהּ מְטַמְּאָה בְבֵית הַבְּלִיעָה. לֹא הָיָה פְסוּלָהּ בַּקֹּדֶשׁ, מְטַמְּאָה בְבֵית הַבְּלִיעָה. וְכָל הַפְּסוּלִים שֶׁמָּלְקוּ, מְלִיקָתָן פְּסוּלָה, וְאֵינָן מְטַמְּאוֹת בְּבֵית הַבְּלִיעָה:
If one ֹpierced [the neck of a bird] with his left hand, or [did it] at night, [or] if he slaughtered non-consecrated animals inside the Temple courtyard, [or] consecrated animals outside the Temple courtyard - these do not render a person impure through swallowing [as is the case with the ingestion of impure kosher birds]. If one severed [the head] with a knife, [or] if one pierced [the neck] of a non-consecrated [bird] inside the Temple courtyard, [or that of] a consecrated [bird] outside the Temple courtyard, [or the necks of] turtle-doves that are not yet old enough [to be sacrificed, or those of] pigeons that are too old [to be sacrificed, or that of a bird] whose wing has dried out, or who has a blind eye, or whose leg was cut off - these render a person impure through swallowing. This is the general rule: Anything that was made invalid inside the Temple courtyard does not render a person impure through swallowing. If it was not made invalid inside the Temple courtyard [but outside], it does render a person impure through swallowing. [In all cases where] ineligible people pierce [birds' necks], their piercings are invalid, but [the birds] do not render a person impure through swallowing.