Remember, many of those photos can be from captive birds and there will be HUGE variations depending on when the beak was last coped. Coping involves cutting back the beak and reshaping. In captivity, most raptors do not seem to wear down their beaks like they do in the wild. Not to say that the birds in the wild will also have variable sized beaks, depending on what stratum they are "wiping" their beaks off after eating.
Rich, this is just amazing, I am seriously loving this sculpture!