To get a clearer sense of the bird's head before I attempted to carve it, I made another model, just of that part.
It's worth stressing this: the big model I made initially helped me with the big picture. However, if I need to, I'll aways make a specific model so I can understand and visualise some specific part better. Rather than just carving away and hoping for the best. (Hope is not a plan!)
Still thinking 'Bluetit' at this stage - but not for long! The problem with carving a colourful creature in a bland wood like lime, without any intention of painting, is that all the colour clues you need for its identity are lost. It would be the same if you make your subject in bronze. Some birds have a characteristic shape that makes them easily identifiable - a wren for example - but not this one. Well, not that I could pull out of the hat. So LBJ, AKA Sparrow, it became.
Don't forget that birds have necks...