Chullin, Chapter 3, Mishnah 6. The final two mishnayot of the chapter turn to a new subject: the physical signs by which we identify that an animal or a bird belongs to a kosher species.
The mishnah opens with the animal kingdom: "Simanei behema vechaya", the identifying marks of the domesticated animal and of the wild animal, "ne'emru min haTorah", were given in the Torah itself. Two marks are involved: a hoof divided completely in two, and the bringing up of the cud. So the pasuk teaches: "Zot hachaya asher tochelu", this is the living thing you may eat, "mikol habehema", of all the animals "asher al ha'aretz", that are upon the earth: "kol mafreset parsa", whatever has a hoof, "veshosa'at shesa perasot", cleft right through into two separate hooves, "ma'alat gera babehema", and which brings up its cud among the animals, "ota tochelu", that is what is permitted to you.
Behema and chaya, the domesticated animal and the wild animal, share the identical pair of signs: a fully divided hoof and the bringing up of the cud.
Signs alone, or also a tradition?
Although these two signs appear in the Torah itself, there are halachic authorities who hold that signs are not sufficient on their own. In their view we also require a mesorah, a received tradition, that this particular species is kosher. Without such a tradition the animal may not be eaten even if both signs are present.
Birds: no verse, but a rabbinic list of signs
"Vesimanei ha'of lo ne'emru" - regarding birds, the Torah records no signs at all. "Aval amru chachamim" - but the Sages taught signs of their own. The Torah provides a list of forbidden birds, and by examining the characteristics common to the birds on that list, the Chachamim were able to formulate the marks that distinguish a kosher bird from a non kosher one.
"Kol of hadores tamei" - any bird that seizes its food with its claws, lifting it off the ground and eating it while holding it, is non kosher. Every one of the birds enumerated in the Torah as forbidden behaves in this way.
From here the mishnah turns to features that point toward kashrut, and it names three of them: "etzba yeteira", "zepek", and a "kurkevano niklaf". A bird in which these are found is "tahor":
- Etzba yeteira, an additional toe: a toe growing out of the back of the foot, sitting higher up than the rest. Nearly every bird has one, and it is called "additional" only because it is not aligned with the toes that face forward.
- Zepek, a crop: a pouch at the upper end of the gullet in which food collects before digestion begins and it moves along the digestive system.
- Kurkevano niklaf, a gizzard with a lining that peels away: the gizzard is a muscular sac that mills the bird's food. If its inner membrane can be separated from the flesh with the fingers alone, without recourse to a knife, that bird is tahor.
A kosher bird will display one or more of these three features. The trait of being doreis, snatching its food, however, overrides everything: a bird that snatches remains forbidden even when all three positive features are found on it. Kashrut is established only where the bird does not snatch and it shows an additional toe, or a crop, or a gizzard whose lining peels away.
In practice, however, even a bird that does not seize its food and carries all three of these signs is not eaten unless we have a mesorah that this species is kosher. This is the position of the Tanna Kamma.
The view of Rabbi Eliezer beRabbi Tzadok
The mishnah closes with a further opinion. Rabbi Eliezer berebbi Tzadok rules that "kol of", any bird, that is "cholek et raglav", that separates its feet, is "tamei". What sort of bird is meant? One which, upon settling on a branch or on any thin ledge, grips it with two toes in front and two toes behind. In his opinion such a stance is itself proof that the bird takes hold of its prey in its talons, and no bird that perches this way can ever be reckoned among the kosher species.