If you catch one of the legendary birds before beat elite four can still Suicune in fire red?

You can still catch Suicune in FireRed even if you catch one of the Legendary Birds before beating the Elite Four.

Here's why:

* Suicune's appearance is not dependent on your progress through the game. Suicune appears in the same location (the Ruins of Alph) after you've completed the main story, regardless of whether you've caught any Legendary Birds.

* The Legendary Birds are not necessary for Suicune's appearance. There's no connection or prerequisite between the two sets of Pokémon.

Therefore, feel free to catch Articuno, Zapdos, or Moltres before facing the Elite Four. Suicune will still be waiting for you in the Ruins of Alph after you complete the main story.