I wonder if local birds to specific areas might be more of a hook than exotic birds, especially if you want the educational part to be more relevant to the person doing the coloring. Coloring birds from the other side of the world might provide for some interesting coloring, but learning about local birds might have more of a hook in the long run. I also think it'd be easier for kids to identify with local birds that they see regularly when it comes to coloring them. Then again, local birds might be too boring to be an actual hook for marketing purposes. Whatever hook you try for, I'd suggest directing it at the adults purchasing the coloring book and not the children coloring in them. If you go with an educational hook, remember to keep things age relevant. Just some quick thoughts, as requested.