I might want to change the place of the bird on the sheet, adjust the
roundness of the belly, (I like chubby birds) or make the bill longer/shorter. Personally I always think sketching shouldn't take too long. Colors will eventually create the bird, but I always have to tell myself; if everything looks good on the sketch, then it will be much easier to make the bird better in a later stage.
Here's the color pallette of the male rufous hummingbird. I like working randomly with colors. When I need one, I will mix one up, instead of getting back to an orange I have used before. This will make it look more alive, I think. So in the end there may be 50-100 types of orange in one bird.