Are you wondering just as much as I am about the specific location of each rare Pokemon when released?
While especially eager players have mined the code of Pokemon GO and confirmed that these legendary Pokemon are indeed in the source code, the continued elusiveness of the “Legendary Pokemon” has proved common ground for a number of fan theories on what Niantic has planned for them in future updates.
These are fan theories, we are not claiming anything, so please read before you comment
Legendary Bird Pokemon
The significance of the three birds as the emblems of the game’s three teams – Moltres for Valor, Articuno for Mystic, and Zapdos for Instinct. While many at first thought little of this detail, Niantic CEO John Hanke has since hinted that players will only be able to catch the particular Legendary Bird associated with their own team. As more light is shed on the importance of the team system in gameplay, most notably in gyms, it’s not too far of a stretch to consider that one way of making your team’s Legendary Bird to appear might be to capture a certain amount of gyms within a given time. I’ve also seen an amazing fan idea, where you collect the feathers of your teams Legendary Bird by beating gyms and visiting Pokestops, which you will be given the feather as a rare reward. Once you’ve found all required feathers and give it to the gym leader, you’ll be given an option to battle the Bird Pokemon and catch it.
Mew & Mewtwo