It looks good... at first.
On close examination, it has some issues.
For one thing, the image and the reference do not look similar. Even if you didn't want to have a carbon copy, you left out some details that are unique to Red Tailed Hawks.
The shape of the beak is off, and it's missing the black spot at the end of the beak. (The tip of the beak curves back in your art, but in the photo it just goes down without curving back.)
The white spot behind the eye socket doesn't hug the eyeball like it doe sin the photo.
The feathers look really erratic. I blame it on the static. You should make it less spastic. Yo. (The feathers are just random placements of pixels. It looks good at first glance, but when you look at it for a second it looks wrong. Feathers can be generalized.)
The shape of the back of the head doesn't look like the bird. (It should have a sharper curve.)
Another issue, the feathers on top of the ears on birds is usually very thin and wiry so that they can hear through them. You can see this in the photo.
In your image the feathers look the same all across the head.
Something else, birds in general back black eyes. Their (usually) brown irises only show when light is reflecting off of them at the right angle, or in sunlight. This means that your eyes are a bit too bright.
I started here.
I went ahead and changed the beak and eyes to look more like the reference, even if you didn't want it to be exactly the same.
I wiped out all of the feathers, because to be honest, they made no sense.
I then laid out the basic sections of the feathers. Over the ears it's lighter, over the eyes it's a lot lighter, and everywhere else it's kind of the same.
I also (tried to) removed some banding that was spread out across the piece.
Remember: No matter how photo-realistic you want your image to be, you have to start somewhere.
Cartoony drawings are like outlines for research papers, it helps a lot to have one.
I touched up some parts of the image, and from there I just scribbled some lines to show some direction, and added in some more shading.
(Also, what was with that dithering outside of the border? )Oh, it was AA for the transparency. Nevermind.
EDIT: