Mishnayos Taharos Perek 1 Mishnah 2

מיטמאות (become susceptible to uncleanness) – if a creeping animal touched them (i.e., the large feathers and down) they are defiled. And if they are impure, and the large feathers and down touched pure foods, they are defiled. For they are considered a handle to bring in and to remove/take out, and anything which is a handle becomes susceptible to becoming defiled and defiles.

ולא מצטרפות (but they do not join together) – if the food was less than an egg’s bulk, the large feathers and the down do not combine to complete it to an egg’s bulk to defile through the ritual impurity of foods, as is taught in the beginning of [Tractate] Uktzin (see Chapter 1, Mishnah 1 – as it is not considered a protective part of the plant).

הנוצה מצטרפת – for it is considered like a protective part of the animal. But the Halakha is not according to Rabbi Yishmael.

החרטום (nose/beak) – that the bird gnaws/bites it.

ראשי אגפים הראש הזנב (tips of the wings and the tip of the tail)- that remain attached to the body after it plucks off the down, and it is customary to cut/sever them and cast them away for they are not appropriate for eating. But on the fattened birds, we leave them and eat them with the bird, and that is what it states [by Rabbi Yossi at the conclusion of the Mishnah]: "שכן מניחים בפטומות"/”for so they are allowed to remain on fattened birds.” But the Halakha is not according to Rabbi Yossi. And these thirteen matters that are considered in our Mishnah, in the first section, there are night, for its ritual slaughter and its pinching/wringing of the neck are considered one, and both of them are pure for its torn animal, and the large feathers and the down and the nose/beak and the nails a, these [make up] the thirteen matters.