I think the reason the birdman is difficult to read is how close the beak is to touching the shoulder. It is one pixel away. This leads the mind to fill in the rest of the rather perfect circle of negative space so it looks like a man wearing a helmet with a visor like an astronaut rather than the white being negative space.

My suggestion would be to at least to move the head and neck over a few pixels so the beak is no longer in line to create a circle with the shoulder and there is a more easily readable silhouette.

I tried to make the shading on the sword look more organic rather than bands of color.

Idk, this is how I would try to approach it, but I always have difficulties with colors and using outlines partly seems to help.

First of all, your picture isn't considered pixel art just because you used some brushes/filters and have so many colors. Typically in pixel art each color is hand-picked. But, that's no big deal. Easy to fix; just draw over it with a pencil tool or opaque brush tool with no auto-aa.

*edited to change the host of the picture; it wasn't showing up on the forum

Bear in mind, I'm not artist and haven't studied lighting in any detail. But, it seems to me most of the object would be in shadow. It may have an outline of light that is coming around the sides. The leaves would be quite bright because they are translucent so the light can get through. Maybe through the ugly smudgy edit I made, you'll get a general idea of what I'm trying to convey.

That picture still is of a grizzly bear, not a black bear.