To get a nest ball go to pattern bush to the last line of grass at left. Use sweet scent. A her across should come catch it. An go to the one who's home has a sign saying:
Wanted! The Ultimate Horn. She should be in water path she will measure your her across (it must be in your party) the she will say: WOW! I've never seen a size like that. And she will reward you by a nest ball.