This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鶮 combines 高 (tall, high) and 鳥 (bird), but the exact historical development is uncertain. It may have originally referred to a tall bird, but this is speculative.
The kanji visually combines 高 (tall) and 鳥 (bird), so you might imagine a tall bird, but its actual meaning is unclear.
For コク, imagine a tall bird making a 'kok' sound: kok -> コク, though the reading is not tied to a clear meaning.