The weak lighting and contrast pervade my first impression. That's all I really see. Though, the bird's form seems more like a hawk for some reason, it's more beneficial for you to walk away with better lighting skills than eagle drawing skills. Why not have some spread wings going on and maybe have him going "CaaaaaahHHHHH!!!" like eagles do. He's just sitting there on a twig. Body is full boring frontal, head is full boring profile. Not dynamic, my friend.
Your lighting could improve. I'm happy that pixelation here has been a good tutor in heightening my appreciation for respecting light. A pixel forum seems like an unlikely source for this, but generally, pixel art peices are rather simple - it being the art of the sprite - so it becomes essential to get these basic things right or there's just not much left to impress your viewer. So . . . your lighting here weakens the impact. How would you shade your eagle if it was totally smooth and had a matte surface? I think you should improve your lighting before worrying about feathers/texture.
Outdoors, cloud-cover may disperse sun light enough to give this non-directional omni-lit look, but that's if this eagle is set in a scene, which it isn't. Since this is a lone sprite, boost it's visual interest with more poignant lighting.
Really though, I think all this is just a symtpom of artistic methods teathered to limited rails. By that I mean, your means of creating images may be too systematic and methodical, stunting and limiting your skill growth. At least, this is a common thing in art. I'm guilty of it, too. Not trying to patronize. Helm was in Bruce Lee mode once recently and said something like, "dont be afraid to destroy your art in order to promote improving". Meaning, don't hold your drawings as sacred and be afraid to "hurt" them. You will often fail as an artist. I do, all the time. But I'll try something else and it eventually works. Sometimes it's brilliant, sometimes it's mediocre. Roll with the punches. I think this eagle may be a failed attempt. If every project we embark on is another step on the staircase to artistic perfection (a never-ending flight obviously, but each step offers new possibilities) you might not be lifting up your foot yet. Notice the words of Hokusai, one of the ancient Japanese masters,
"From around the age of six, I had the habit of sketching from life. I became an artist, and from fifty on began producing works that won some reputation, but nothing I did before the age of seventy was worthy of attention. At seventy-three, I began to grasp the structures of birds and beasts, insects and fish, and of the way plants grow. If I go on trying, I will surely understand them still better by the time I am eighty-six, so that by ninety I will have penetrated to their essential nature. At one hundred, I may well have a positively divine understanding of them, while at one hundred and thirty, forty, or more I will have reached the stage where every dot and every stroke I paint will be alive. May Heaven, that grants long life, give me the chance to prove that this is no lie."
Rock on. CaaaaaaaHHHHhhhhhh
