You can catch one of the Legendary Bird Pokémon in Pokémon X/Y. Which one it is depends on your starter. If you chose Chepsin , you'll be able to catch Articuno ; if you chose Fennekin , you'll be able to catch Zapdos ; and if you chose Froakie , you'll be able to catch Moltres .
No matter which bird you can catch, it flies randomly around Kalos , appearing in different places. If it's in a certain place, you'll sometimes bump into it at that place when walking through flowers or grass. To actually catch it however; you need to see it numerous times in the wild (like, ten or possibly more).
After seeing it the first time though, you'll be able to track where it is by checking its habitat under its entry in the Pokédex. You can then just follow it around and keep trying until you see it plenty of times. Once you have seen it a heap of times, head to the Sea Spirit's Den , as the bird will be there waiting for you.
Sea Spirits Den
If you've seen the legendary bird enough times, it'll be here waiting for you. As before, **** save the game before you battle **** it as you only get the one chance to catch it! If you end up failing, restart the game and try again until you do. Bring heaps of Ultra Balls or a Master Ball if you have it. Once you're ready, interact with it and the battle will begin!
Legendary Pokemon Battle
Obviously, you'll want to catch this guy - short of trading, you'll be lucky to find this Pokémon again. The sure-shot method would be to use the Master Ball . However, the Master Ball is a one-time item that you'll want to save for more annoying Pokémon that just have to run away from you. Or at least more powerful Pokémon.
The other way? Teach a Pokémon to use Thunder Wave or Stun Spore and False Swipe . Either of the first two moves can be used for Paralysis, which boosts catch rates. False Swipe is a 40-Power Normal move that won't kill. (If you can't use it, try moves that deal less damage than normal: it's riskier, though!)
You can try using False Swipe for two turns after Paralysis is induced to try and see how well the quadruple-rate Quick Ball will do on this fourth turn. If it fails, then just lower the Pokémon's HP to 1 and then begin shooting Ultra Balls at it.
Keep track of turns , though - after 20 turns pass, the Timer Balls will begin to be more effective. They have a x3.0 catch rate at that point (Ultra only is x2.0 ), but if you're low in number, you may want to wait some more until they're up to x4.0 later. Dusk Balls also work, since you're in a cavern.
(For the record, status-wise, Sleep and Frozen are 33% more effective to the catch rate than Paralysis . However, neither stat is permanent without curing, and no move causes Freezing without damaging the Pokémon.)
Note : Zapdos, being an Electric type, is immune to Paralysis. So Sleep is your best bet to catch Zapdos, despite the possibility of Zapdos frequently waking up. If you have it, the Capture O-Power (especially at Level 3) is good to have.
Once it's caught, head back outside. Feel free to do whatever you want!