STEP 1: After you have beaten the game and unlocked the national pokedex, go to Eterna City. Go to the house that is nearest to Cycling Road. In the house, you will find Prof. Oak.Talk to him and he will say something about the legendary birds, Articuno, Zapdos, and Moltres. When you're done, go to the map app on your pokedex. There will be figures on it. These are the legendary birds. STEP 2: The easiest way to catch the birds is to go to two different Routs that connect. (ex: 210 and 215.) run between the Routes and check your pokedex each time until one of them is on your Route. Do this for each one. Hope this helped!