Big Birthday!
Happy birthday!
The likeliest bird for your mystery stripy warbler is probably Black-throated Gray Warbler. There aren’t a lot of them around, but there are definitely a few. (I saw my first of the year a few days ago.) Another possibility is Black-and-white Warbler. That would be a significantly rarer bird, but still possible.
Black-and-white Warbler has a characteristic foraging style of creeping along trunks and branches like a nuthatch. It also has a slightly droopy, downward-curved beak. Black-throated Gray is more of a “typical” warbler in the sense of having a straight beak and a foraging style of flitting around in foliage.
There are some other differences in their appearance that are pretty obvious once you know what to look for. Black-and-white Warbler has longitudinal striping over the top half of the head; basically a really stripy black-and-white crown. It continues that pattern by having bold black-and-white longitudinal stripes on its back. Black-throated Gray has a solid crown but big, curvy, white stripes across the face. They also sometimes have a little yellow spot in front of the eye, which is hard to see but distinctive if you do see it. They have more of a solid gray on the back.
Checking the eBird histogram for the Salesforce Park hotspot, it looks like there have been reports of Black-throated Gray Warbler there before, so that definitely seems like a possibility. Yours would be the first reported sighting outside of fall migration, though, which would be kind of exciting.
Reposted from https://lies.tumblr.com/post/673273979257192448.
