Mishnayos Negaim Perek 14 Mishnah 5

With regard to the two birds: the commandment is that they be alike in appearance, in size and in price; and they must be purchased at the same time. But even if they are not alike they are valid; And if one was purchased on one day and the other the next they are also valid. If after one of the birds had been slaughtered it was found that it was not wild, a partner must be purchased for the second, and the first may be eaten. If after it had been slaughtered it was found to terefah, a partner must be purchased for the second and the first may be made use of. If the blood had been spilled out, the bird that was to be let go must be left to die. If the one that was to be let go died, the blood must be spilled out.

שְׁתֵּי צִפֳּרִים מִצְוָתָן שֶׁיְּהוּ שָׁווֹת בַּמַּרְאֶה וּבַקּוֹמָה וּבַדָּמִים, וּלְקִיחָתָן כְּאֶחָת. אַף עַל פִּי שֶׁאֵינָם שָׁווֹת, כְּשֵׁרוֹת. לָקַח אַחַת הַיּוֹם וְאַחַת לְמָחָר, כְּשֵׁרוֹת. שָׁחַט אַחַת מֵהֶן וְנִמְצֵאת שֶׁלֹּא דְרוֹר, יִקַּח זוּג לַשְּׁנִיָּה. הָרִאשׁוֹנָה מֻתֶּרֶת בַּאֲכִילָה. שְׁחָטָהּ וְנִמְצֵאת טְרֵפָה, יִקַּח זוּג לַשְּׁנִיָּה. הָרִאשׁוֹנָה מֻתֶּרֶת בַּהֲנָאָה. נִשְׁפַּךְ הַדָּם, תָּמוּת הַמִּשְׁתַּלַּחַת. מֵתָה הַמִּשְׁתַּלַּחַת, יִשָּׁפֵךְ הַדָּם: