Rashi on Leviticus 22:8/רש"י על ויקרא כ״ב:ח׳

1נבלה וטרפה לא יאכל לטמאה בה CARRION, OR THAT WHICH IS TORN HE SHALL NOT EAT TO BECOME UNCLEAN THEREBY — It is with regard to the defilement that Scripture lays down this prohibition: that if he (the priest) eats the carrion of a clean bird — which has no defiling effect through being touched or carried but has a defiling effect only when eaten, as soon as it is in the gullet — he is forbidden to eat holy things (Sifra, Acharei Mot, Chapter 12 6). And it was necessary for Scripture to mention טרפה also, in order to define what נבלה is here intended, viz., one that can have a טרפה amongst the individuals of its class: therefore the נבלה of an unclean bird is excluded, for in its class a טרפה can never occur (cf. Rashi on Leviticus 17:15).