If I may toot my own horn for a second, I'd like to piggyback onto Ted's post and mention that in the Colorado Birds Fall 2021 issue (v55, No 4), I had an article titled "The Sincerest Form of Flattery" where I discussed the phenomenon of mimicry in bird songs in Colorado. Like Ted, after giving due credit to the main mimicry culprits like Northern Mockingbird and Yellow-breasted Chat, I mentioned the Lesser Goldfinch as a "lesser known" mimic that deserves more recognition than it has received for its intriguing imitations. Referenced therein is another Colorado Birds article from our own Hugh Kingery in 2004 where he tallied 25 different species being imitated by LEGOs based just on his observations in the state! Sharon Goldwasser's 1987 Master's thesis documented 39 different species being imitated by Lesser Goldfinches in Arizona, including Tufted Flycatcher.
In fact, one needs to be cautious in the vicinity of LEGOs for they will also imitate other finches, both calls and songs. Just the other day during my field season I was initially snookered by a LEGO inserting occasional Evening Grosbeak sounds into its calls and songs.
Good birding to all,
Eric
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Eric DeFonso
Boulder County, CO