Hi there,
Grinning birds! I love grinning birds, I wonder why they are not used more in cartoons.
I think the current problems here is that there are not enough details that indicate us it is a bird, despite being cartoony.
The first noticeable thing is the lack of a beak, or assumptiosn of it. There needs to be more sorrounding the teeth, even if it is just a little orange here and there so it is kind of implied.
Overall anatomy, many common birds have "fat" bodies (I quote it, because -more often than not- it is just an illussion given by the feathers) and narrow heads, and short legs and long feet.
About shading, there is a lack of a clear light source on the body, while on the head it comes from the top left (from our perspective). I think the colors need a little changes, but I'll let someone more educated on the field explain about it (or point out to
arne's art tutorial).
I did a quick dirty job addressing those points, inspired for the most part by Squit from the
Goodfeathers. I apologize if it strayed too far from what your intention of depicting is:
Yours - edit
