Here are some ideas for search terms to use in a Google Search to find CREDIBLE websites.
I am using “owl” as my example object:
Search example: “examples owl symbolism in literature”
Search example: “owls in literature”
Bad results: Quora; Reddit subs; study sites; social media
A Dictionary of Literary Symbols, Michel Ferber (Internet Archive)
(search on “______ symbolism”). Fairly general and LOTS of ads, but sometimes some good info can be found here
Do a search on your object and Shakespeare: There are many natural symbols and motifs in Shakespeare’s works
Most of the sources linked in other boxes will also give the associations that your object has. You can also try a Google Search: [object] as a positive symbol or [object] as a negative symbol.