This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鵇 combines 年 (year) and 鳥 (bird), but the exact historical development and original meaning are uncertain. It may be a kokuji created for a specific bird name.
The kanji visually combines 年 (year) and 鳥 (bird). Without a clear meaning, you might picture a bird that appears at a certain time of year, but this is only a mnemonic guess.
For とき, think of a bird that appears at a special time (とき): the bird 鳥 arrives with the year 年, marking the right time とき.
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