Does intuitionistic logic challenge LEM but not LB?

I think this is the case because:

1. Someone says to you "That bird is white"
2. You can't see the bird.
3. You don't have constructive proof it is white or not white.
4. LEM challenged/broken

However, with the law of bivalance:

1. Someone says to you "That bird is white"
2. You can't see the bird.
3. Regardless of not knowing if the bird is white, the truth value of that proposition must be either true or false.
4. LB unchallenged.

Do I understand this correctly or is there a big flaw in my understanding of intuitionistic logic? Thanks in advance