Wa alaykum salam wa rahmatuLlahi wa barakatuHu,

Feathers plucked while an edible bird is alive, or after it is slaughtered, are pure. If the feathers are from an inedible bird, or plucked from an edible bird after it dies without being slaughtered, then they are impure. In the instance that one doubts the source or whether they were taken before or after slaughter, then the default ruling is that they are pure. (Mughni al-Muhtaj v. 1, p. 235; Tuhfat al-Muhtaj v. 1, p. 300)

And Allah knows best.

Shafiifiqh.com Fatwa Dept.