This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鵼 combines 空 (sky, empty) with 鳥 (bird). The exact historical development is uncertain, but it likely refers to a mythical bird or a bird associated with the sky.
A bird (鳥) in the empty sky (空) — a mysterious creature with no fixed meaning.
For コウ, imagine the empty sky (空, くう) where the bird flies: 空's reading コウ cues コウ for 鵼.