The base sign for bird forms the basis for many bird signs, so is a radical. It is also morphed through mimicry into the parrot sign which is then used as a base radical for signs like budgie. We have put both radicals in one group here. Basically the pointer thumb extrented and touching (or opening and closing) near mouth means bird. It carries that meaning through into the use of all fingers for large beaked birds, and hooked pointer for parrot species.