Thank you for the critique. And if I get the chance, I'll try to improve this one.

There's a number of issues here. It's a difficult task anyway!

First thing, the reference isn't an easy one to work from, mainly because the bird position is not as staightforward as it may seem at first glance. It's probably taking a sharp turn to the right so its body is tilted; it's not clear whether we see the top or underside of the tail but I'd go for underside. Also there is potential shading confusion because highlights on the dark feathers have the same value as the brighter body; the rather frontal light makes it hard to read volumes and would not really allow for a nice shading with few colors. However, you didn't make the best use of what you've got: look better!

Anatomy is wrong: the head is way too big, wings too short, shoulders too far backwards.

The body has no volume: the main clue in the ref is the strong underside shadow that you missed. Similarly, there is a tiny but important shadow line on the wing edge ('upper arm'). Other subtle but important clues: the play of shadow and highlight on the head and around the eye.
Do not even think about texturing until you have blocked the volumes right!

Wing detail: the lower left part ('upper arm' again) detail in the ref is too complex and tiny to be realistically pixeled, what you did looks like scales instead. Not sure without trying but I think it would be best left flat.
The ref quills have nicely dynamic, un-symetric curved or straight edges: these might be pixeled better at least for the near vertical quills.

Colors: the saturation by itself isn't a problem, what might be is that it looks similar for all colors. Also crows do have fascinating hues that just need a little enhancing ;)

Keep'em coming!