crow, raven
鴉 centers on the crow or raven, the large black bird. The two meanings are essentially the same animal, with no distinct conceptual split.
common raven (Corvus corax)
jungle crow (Corvus macrorhynchos)
carrion crow (Corvus corone)
The Raven (narrative poem by Edgar Allan Poe)
winter crow
crow cawing in the morning; crows crying in the morning
blacker than black
glossy black (hair); color of a crow with wet feathers
jet-black hair
Australian magpie (Gymnorhina tibicen)
鴉 combines 牙 (which likely contributes the sound) with 鳥 (bird), forming a phono-semantic character for the crow or raven.
A bird (鳥) with a tusk-like beak (牙) that caws loudly: that's a crow or raven.
For ア, imagine a crow opening its beak wide and letting out a loud 'Ah!' sound: 'Ah!' -> ア, the crow's cry.