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1. A Tor is a Kosher bird, since it has all four Simanim of Taharah: an extra toe, a crop, its gizzard can be peeled, and it does not claw and eat.
2. Any bird which has at least one of the four Simanei Taharah is Kosher, with the exception of those listed among the non-Kosher birds.
3. The Peres and Ozniyah, which are listed in the Torah among the non-Kosher birds, have one Siman Taharah each, but each has a different Siman than the other.
4. The Tor is mentioned in the Torah as a Kosher bird in order to teach that it may be brought as a Korban.
A BIT MORE
1. The Simanei Taharah for birds are mid'Rabanan. The Torah does not list Simanei Taharah for birds; rather, it names the non-Kosher birds, and any bird not included in the list is Kosher.
2. Twenty of the birds that are listed in the Torah have three Simanei Taharah, the Orev has two Simanei Taharah, and the Peres and Ozniyah have one Siman Taharah.
3. If not for the fact that the Torah lists the Nesher among the non-Kosher birds, teaching that a only a bird which lacks all of the Simanei Taharah is non-Kosher, we would have deduced from the Nesher and Ozniyah that even a bird with one Siman Taharah is Kosher.
4. Since the Tor has all four Simanei Taharah, it was not necessary for the Torah to teach that it is Kosher. It was necessary for the Torah to teach that it may be brought as a Korban since, of all of the birds, only the Tor and Ben Yonah may be brought as a Korban.
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