When we first bought this house the yard was full of stickers. Some farmer told us to put something on it from feed store but idk what it was I have to ask james. We didnt do it we just kelp it mowed and watered the crap out of it so far we have kelp stickers down and it is actually getting nice in the yard.
You don't want to put down what I think this guy is talking about if you let your birds free range. I can't remember the name of it, but I know it is not good for any animals. Try white vinegar, full strength. If this doesn't work, try bleach. Keep animals off of it for at least 24 hours, as long as it is sunny. Sun will burn off chlorine, and it will be safe.