This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鴲 combines 旨 (delicious, principle) with 鳥 (bird). The exact historical development is uncertain, but it likely originally referred to a specific bird species.
A bird 鳥 with a delicious 旨 flavor? Imagine a bird that is considered a delicacy, though its actual meaning is unclear.
For シ, picture a bird 鳥 sitting on a delicious 旨 branch, and you say 'She!' (シ) pointing at it.