nothing really
grovile
Yes you can catch the three Legendary birds in Platinum but you'll have to beat the game first and to minor side activites before hand
The Ultra Ball is the ball with the highest catch rate after the Master Ball.
After you catch them like any Pokemon they are saved on your pokedex and ready for use.
The catch rate for the three legendary birds is 3 in all of the games, including Platinum.
You are stronger of cource by pecy Jackson
After you get the national dex go and talk to professor Oak in Pal Park than he will be in a house in lower left corner of Eterna city and he will say the legendary birds are roaming in Sinnoh than with the help of Marking app you can catch the three legendary birds
because they fly around and roam so you can catch them (like mesprit and cresselia)
You can catch Articuno in the Seafoam islands (Kanto), Zapdos at the Power Plant (Kanto), and Moltres in Mt. Silver (Johto).
Its Simple, fly to kanto and search zapdos in:power plant, moltres in:Mt.Silver and articuno in :Seafom island.
Of the three original legendary birds, there is Moltres, and of the Johtolegendary birds, there is Ho-Oh.
you have to beat the elite 4 again and then they will start roaming again and you can try 2 catch them. (: