To respond to Chris Kessler
"And while the Red-flanked Bluetail has been well documented and plainly
here, I note that the previous sightings on eBird are in West Coast cities
except for two inland western sightings, leading me to wonder if these are
not either ship-assisted birds or released/escaped "pet" birds. Still a
very cool bird, but have to wonder how it got here

I'd be interested in others' thoughts on either issue"

Remember the issue of viewer/sampling bias in Ebird- ebird reports come
from where the birders are, not where the birds are. The sample will always
be highly biased towards areas with lots of birders or popular sites that
get birded regularly. Also, rarities will be seen more in areas with
experienced birders who have them brought to their attention.
You can also search for how prevalent birds are in cage populations, and
few highly migrant insectivores like this are kept in captivity.
--
James Neitzel, Ph.D.
Member of the Faculty, Biochemistry
The Evergreen State College