Okay, the first one doesn't have any feet, the bottom two do, so you could try and copy that... BUT I'd say that you should try first drawing it in separate, traditionally, on a piece of paper, to understand how bird feet work, their forms, etc. Then you would translate that to pixel art.
EDIT: Sorry, I forgot to say: using photos of real birds as reference.
It could be a bit of work, but I feel it's the correct way to approach it. Others will most likely have a different opinion (I hope they'll chime in).