It does not change shape or size once it has fully grown, though some birds do have casques that vary during the breeding season. Casque: This hard, horny structure may be either on the top of the bird's bill or on the top of the head.It never, however, dangles over the bill and is not floppy or flexible. Basal Knob: This is an engorged, round structure at the base of the bill, but it is typically hard and does not change color or size as frequently as the snood, though it may change somewhat in breeding birds.The cere never dangles longer than the bird's bill. The cere may swell if infected, but does not dramatically change color or size as the snood will and is more often completely flat or only slightly bulbous.
Cere: This is a fleshy patch of skin covering the base of the bill and often covering the nares (nostrils).
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