Chulin3: 5
אֲחוּזַת הַדָּם, וְהַמְעֻשֶּׁנֶת, וְהַמְצֻנֶּנֶת, וְשֶׁאָכְלָה הַרְדּוּפְנִי, וְשֶׁאָכְלָה צוֹאַת תַּרְנְגוֹלִים, אוֹ שֶׁשָּׁתַת מַיִם הָרָעִים, כְּשֵׁרָה. אָכְלָה סַם הַמָּוֶת אוֹ שֶׁהִכִּישָׁהּ נָחָשׁ, מֻתֶּרֶת מִשּׁוּם טְרֵפָה, וַאֲסוּרָה מִשּׁוּם סַכָּנַת נְפָשׁוֹת.
[An animal] that is seized with blood, or that inhaled smoke, or that was overcome by the cold, or that ate oleander, or that ate the dung of chickens, or that drank bad water, it is fit. [If] it ate poison or [if] it was bitten by a snake, it is permissible insofar as treifah is concerned, but it is prohibited because of danger to life.
Chulin3: 6
סִימָנֵי בְהֵמָה וְחַיָּה נֶאֱמְרוּ מִן הַתּוֹרָה, וְסִימָנֵי הָעוֹף לֹא נֶאֱמְרוּ. אֲבָל אָמְרוּ חֲכָמִים: כָּל־עוֹף הַדּוֹרֵס, טָמֵא. כָּל־שֶׁיֶּשׁ־לוֹ אֶצְבַּע יְתֵרָה, וְזֶפֶק, וְקֻרְקְבָנוֹ נִקְלָף, טָהוֹר. רַבִּי אֱלִיעֶזֶר בַּר צָדוֹק אוֹמֵר: כָּל־עוֹף הַחוֹלֵק אֶת־רַגְלָיו, טָמֵא.
The characteristics of animals and beasts were stated in the Torah, but the characteristics of fowl were not stated. The Sages, however, said: Any bird that seizes its food is nonkosher. Any one that has an additional toe, a crop, and its gizzard can be peeled, it is kosher. R’ Eliezer bar Tzadok says: Any bird that parts its toes is nonkosher.
Chulin3: 7
וּבַחֲגָבִים: כָּל־שֶׁיֶּשׁ־לוֹ אַרְבַּע רַגְלַיִם, וְאַרְבַּע כְּנָפַיִם, וְקַרְסֻלַּיִם, וּכְנָפָיו חוֹפִין אֶת־רֻבּוֹ. רַבִּי יוֹסֵי אוֹמֵר: וּשְׁמוֹ חָגָב. וּבַדָּגִים: כָּל־שֶׁיֶּשׁ לוֹ סְנַפִּיר וְקַשְׂקֶשֶׂת. רַבִּי יְהוּדָה אוֹמֵר: שְׁנֵי קַשְׂקַשִּׂין וּסְנַפִּיר אֶחָד. וְאֵלּוּ הֵן קַשְׂקַשִּׂין: הַקְּבוּעִין בּוֹ; וּסְנַפִּירִין: הַפּוֹרֵחַ בָּהֶן.
And among locusts: Any one that has four legs, four wings, jointed legs, and its wings cover the greater part of its body. R’ Yose says: And its name must be chagav. And among fish: whatever has a fin and a scale. R’ Yehudah says: Two scales and one fin. These are the scales: those that are fastened to it; and fins: those with which it glides.