On September 9, 2022, Brendan Beers reported a Snowy Plover at Timnath Reservoir in Larimer County, in northcentral Colorado. No previous fall eBird records exist for this species in Larimer County, so this was a truly rare bird. Looking at his digiscoped photo (the first photo in this gallery), the bird struck me as odd for a typical North American Snowy Plover (Charadrius nivosus nivosus). Upperparts were darker brown and legs were darker than I expected. Upon further investigation, I learned that Eurasian sister species Kentish Plover (Charadrius alexandrinus) averages darker than nivosus. Two palearctic subspecies of Kentish Plover could occur as a stray from Europe (C. a. alexandrinus) or Asia (either C. a. alexandrinus or C. a. nihonensis). Other Eurasian plover species are well known to stray to North America on occasion, such as Common Ringed Plover, Lesser Sand-plover, European Golden- Plover and Eurasian Dotterel, so why not Kentish Plover? Click on photos and sonogram images for more discussion. PAGE 1. Images of mystery plover PAGE 2. Comparison of sonagrams of mystery plover to 3 similar calls of Kentish Plover from China and 5 equivalent vocalizations from Snowy Plover. PAGE 3. Kentish Plover reference images for comparison. PAGE 4. Snowy Plover reference images. Note paler legs and pale fringes of upperpart feathers of Snowy Plover. PAGE 5. Side-by-side comparisons of our mystery plover with Kentish and Snowy Plover PAGE 6. Additional photos taken by Nick Komar 10 Sep 2022 with Canon Powershot SX70. Ultimately, the dark brown upperparts, extensive white in rump and tail, and high-pitched flight call support the identification of our mystery plover as Kentish Plover, possibly from Japan or China. The strongest evidence is the sonagram which has a rounded mark at 5.5 KHz rather than a pointed mark at 4.5 KHz (see p.5 comparison).