So after I beat the elite four and everything, I was just messing around, then, randomly, out of nowhere, I ran into Articuno. I was really excited because I forgot I could catch one of the legendary bird trio, and then I remembered I had to chase them. The Articuno ran, and I was sad. But then I started chasing it. I looked at the pokedex and everything, but when I got on the route Articuno is on, it ALWAYS, and I mean ALWAYS, goes to another route! I can NEVER catch it! I've been at it for at least an hour now and this has been happening EVERY TIME!!! D:< Can someone please explain to me what I'm doing wrong!?