Discord: "Why, preening is a practise done by all animals that have wings. You pluck off any pests and loose feathers and of course clean and smooth up your wings, or in this particular case Twilight's wings. It's also a social event done between family, friends and lovers to strengthen the bond and to help the other. ... they're purple wings, they obviously taste like pear split ice cream."
There's the answer for your questions. Thank you for the comment