night heron
鵁 refers specifically to the night heron, a type of bird.
鵁 combines 鳥 (bird) with 交, which likely contributes a phonetic element. The exact historical development is uncertain.
The bird radical 鳥 on the right and 交 on the left can be remembered as a bird that crosses (交) the night sky: the night heron.
For コウ, imagine a night heron crossing a calm lake at dusk, its reflection creating a perfect 'ko' sound as it glides: ko -> コウ.
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