I pick up all trash. Everything that comes in goes out. Usually end up picking way more than what I brought in. On public some people are real a $$holes about leaving trash (not just hulls) which is disrespectful on many levels and can jeapordize our hunting privileges on public.
But a pile of my own shells from taking a full strap or dove vest at a honey hole? Oh, thats a pleasure not a burden! Gotta protect my spots! For that matter i never clean birds at my spot either, I leave my coyote offerings where the birds are not