seagull
鴎 centers on a specific seabird: the seagull. The meaning is narrow and concrete, referring to the bird itself.
鴎 is the modern simplified form of 鷗. It combines 区 (possibly phonetic) with 鳥 (bird) to denote a seagull. The older form used 區 instead of 区.
The left side 区 looks like a coastal area, and the right side 鳥 is a bird. Picture a seagull flying over a coastal district.
For オウ, imagine a seagull letting out a loud 'Oh!' as it spots a fish: Oh -> オウ.
common gull (Larus canus)
northern fulmar (Fulmarus glacialis)
giant petrel (esp. the southern giant petrel, Macronectes giganteus)
Cape pigeon; Cape petrel; pintado petrel (Daption capense)
old sword fighting; sword drawing style or school from Shizuoka prefecture
long-tailed jaeger; long-tailed skua (Stercorarius longicaudus)
glaucous gull (Larus hyperboreus); burgomaster
black-headed gull (Chroicocephalus ridibundus); hooded gull
skua (any bird of family Stercorariidae, incl. the jaegers)
laughing gull (Leucophaeus atricilla)
herring gull (Larus argentatus)
chignon resembling a seagull's spread tail feathers (Edo-period women's hairstyle)
Caspian gull (Larus cachinnans)
parasitic jaeger; Arctic skua (Stercorarius parasiticus)