I have hired an artist to make a voxel model of a bird human and he came up with this:

I've seen that he has looked at pictures of Rito from Zelda: BotW for inspiration. Now I'm wondering whether this model is too similar to the aforementioned Rito and would constitute copyright infringement? On the other hand, Nintendo cannot copyright the idea of making a bird human and some features such as the legs, wings, beak, feathers, etc. are just inspired by actual birds. And it is a voxel model anyway.

What do you think? Is that okay? Should I contact a lawyer?

It could be more than just copyright, although that's what people often think of first. The big three are copyright, trademark, and patents, but they aren't the only legal protections.

If you are concerned, you should talk to a lawyer about your risk.

Infringement cases get complex and get decided by the court. Since it is not a picture-perfect copy of the characters it will be up for interpretation. Generally the big picture taken in context comes into play, not just a single image out of context. A lawyer will help you understand your risks, which will never drop to zero risk.

@Tom Sloper