The legendary birds contains Articuno, Zapdos, and Moltres in the team. Some people believe Lugia and Ho-oh are also part of the bird trio.
You can find Moltres in the Kanto Pokemon Championship.
Articuno when Ash is with the photographer friend of his.
And Zapdos durind Season 5 near a pond.
Anime
You can see them with Lugia in Pokemon: The Power of One
TRIVIA:
- Their names consist of the first three spanish numbers, Articuno, Zapdos, and Molttres. Their National Pokedex numbers go in order from uno to tres, and they are the THREE legendary birds, so that makes sence