Hey East Bay friends! As is abundantly obvious on any trip to our shorelines, it's peak shorebird season right now! That means rarities mixed in with the big flocks, but it also means some subtle identification challenges. One issue that seems to pop up from time to time in our area is worn breeding-plumaged Sanderling vs. Red-necked Stint. At this season, some Sanderlings have a fairly bright reddish face and throat, combined with a mostly drab-colored back, closely approximating the pattern of a Red-necked Stint. This plumage superficially looks more like a stint than like the breeding or nonbreeding plumages of Sanderling shown in most field guides. I've been fooled badly several times, and I know it can be an issue especially when there's a stakeout Red-necked Stint that alot of birders are looking for.
To me the most useful field mark, especially at a distance, is often SIZE. Red-necked Stints are about the same size as a Western Sandpiper, similar in length to that species but sometimes looking slightly smaller due to their slimmer structure. Sanderlings are noticeably bigger than Westerns when seen side-by-side. Sanderling bills are also longer than Red-necked Stint, and the body structure is overall bulkier. The red neck on a red-necked Sanderling is a drabber tone, more of a muted brick-red with black spotting, vs. the cleaner burnt-orange of Red-necked Stint. The back pattern is especially useful: Sanderling backs are very boldly spotted in black, white, and pale grey at this season. There may be some rufous feathers there, but no flat medium brown tones. Red-necked Stints have browner, somewhat less brightly-patterned backs.
Here's a few eBird examples of Sanderlings in red-necked late-summer plumage:
https://macaulaylibrary.org/asset/358219041, https://macaulaylibrary.org/asset/357500281, https://macaulaylibrary.org/asset/356119071
And for comparison, some nice photos of our very own 2017 and 2021 Red-necked Stints at Alameda South Shore:
I'm still learning with shorebirds, and find it useful and enjoyable to write out what I have discovered in posts like this. Hope it's helpful for others too.
Good shorebirding! See y'all out there on the shore!
Noah Arthur (Oakland)