Super simplicy is fine and often great looking. However, the simpler the piece the more presice the pixelling should be as it stands out more than in complicated pixelarts. Here the jaggies stand out a bit too much and take away from its overall impact.
I like the mood you have working here. A few crits on the design aspects:
-The green of the legs is getting lost against the yellow shadow and bg
-The eye would be more dynamic if it wasn't in the exact center of the head. I would offset it a little in the upper-right direction.
- The circular shape of the head overpowers the other less mathematical shapes. It might be worth making it *slightly* ovoid. Making the beak overlap it on the edge would help, too.
-I'm not sure about the way the canvas cuts off the top of the head. There's some trapped negative space between the shadow and the head that causes unintentional tension. There's also a similar little pocket of it to the left of the neck.
-Adding one shade of AA between the dark brown and the lighter shades would help smooth out the jaggies without overcomplicating the piece. Since it's pixel, might as well employ some techniques inherent to the medium.
This piece has great potential!