cockatoo
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鵡 refers specifically to a cockatoo, a type of crested parrot. The meaning is narrow and concrete, with no broader conceptual center beyond this bird.
chambered nautilus (esp. species Nautilus pompilius)
(large) parrot (incl. the cockatoo)
grey parrot (Psittacus erithacus); African grey parrot
kakapo (Strigops habroptila); owl parrot
palm cockatoo (Probosciger aterrimus); goliath cockatoo; great black cockatoo
parakeet auklet (Aethia psittacula)
kea (Nestor notabilis)
鵡 is a phono-semantic compound: 鳥 (bird) provides the meaning, and 武 likely contributes the sound. The character was created to name the cockatoo, combining the bird radical with a phonetic element.
A bird (鳥) with a martial (武) crest: imagine a cockatoo with a striking, warrior-like crest of feathers.
For ブ, picture a cockatoo booing loudly from its perch: boo -> ブ, and the bird's call echoes its reading.