I dunno - there are a lot of cases where bullying can really get out of hand. My inclination is to take it to your parents, so they're aware of what's going on, and document if possible anything that can be documented. However I wouldn't take it much further unless something actually happens; previous posters are right about the fact that some people just like to poke around to see what makes you jump. If you jump, you're entertaining them and giving them reason to poke you again, harder. If you don't react at all they may get bored and look for some other way to keep themselves occupied. However, if they really mean trouble, and actually do you some harm, any documentation you have of the threats they've made will help you get them prosecuted. Most of all, if the people you're telling about your chicken-plans are reacting this way, they're DEFINITELY not your friends and I wouldn't share any more chicken stories with them. Keep it cool, Jack.
Best wishes with your future-chickens!