Originally Posted by
bigbarada
That's something that I've been thinking about since the first LOTR movie. In one way, I kind of wish that they did speak so that audiences would realize that they are a sentient race of beings right alongside elves, dwarfs, hobbits, humans, etc.; but that's a tricky thing to make work in a movie, since birds' beaks are too rigid and can't move in the same way as a human mouth. So, trying to have the eagles' beaks move like lips would be Fakey McFakerson as soon as they uttered their first word. The other option would be to have sort of a "telepathic" speech, where their mouths don't move but you hear their voices. However, then you'd have the question of, "Does everyone hear them or does only Gandalf hear them?" So, I guess it's best to not allow the pacing of the movie to grind to a halt over such a minor detail and keep the eagle's speech out of the film.
Of course, there are still two movies to go. They might speak after all.