It’s not bad, however, the animation is slow. Even at this stage, there is room for improvement. You could study the reference of the motion when the bigger bird flaps its wings. Also, you could also apply a subsurf modifier to the bodies of the multi-color birds.
Now for the mountain scene. The one thing that kinda put me off was the slowdown of, from what I could guess, that the mountain exploding. That part of the video was clearly slowed down but then sped back up to its normal speed. That’s a mistake that can “break the illusion” of the video. You never want to do that.
it’s not the best animating I have seen but enjoyable nonetheless and it’s nice to see a story as opposed to just a simple anim movement test