[All photographs copyright, Gary Nunn 2012] – This warbler was first found by Barbara Carlson and Christine Harvey at the junction of San Fernando and Lawrence Streets in the La Playa neighborhood of Point Loma, San Diego on 18 Nov 2012. Shortly after it was found I went over to the location and obtained some close photographs as it preened and then foraged in small pepper trees. The bird had a structure much like Townsend’s Warbler but looked a bit “off” for that species in my opinion. One immediate difference, apart from the obvious absence (mostly) of yellow in the plumage, was the well defined grey auricular coloration merging without interruption to the nape. It was not separated from the nape by a lighter colored posterior auricular frame, forming a dark auricular patch, like that of Townsend’s Warbler. Also the white throat had below it a dusky gray bib, sort of like a faded “Myrtle” (Yellow-rumped) Warbler. It does seem to have a faint yellow patch on the breast side too – weird. Perhaps the most noticeable difference though came from its call – a low and syrupy churp quite unlike the emphatic sharp chit call of Townsend’s Warbler. In my opinion it sounded very similar to the call of a “Myrtle” (Yellow-rumped) Warbler.
The flight photograph below shows what appears to be three colors to the body upper parts with the rump (yellow-green) contrasting with both the back (olive-green to brownish) and upper tail coverts (bluish-grey). I was concerned the back color was an artifact of the light, but it does also contrast with the bluish-grey scapulars that kind of muddle in to the back color if you look carefully. To my eye also the lower back looks green where it borders the rump – that’s four colors on the body upper parts! Many of the feathers of the upper parts appear to have small dark centers. Also visible on the left wing in the flight photograph are the freshly molted greater and median coverts, with just a few retained and more faded looking greater coverts.
The photographs below of the closed left wing show quite well a couple of the freshly molted median coverts poking out from under the fluffy scapulars. The median coverts have wide black bases but the black tapers quickly to a fine central streak. Based on Pyle 1997 this would seem to indicate this is a hatch year (HY) female, or possibly a second year female Townsend’s Warbler.
Perhaps the bright greenish-yellow rump and yellow feathers on the flank sides point to some type of Yellow-rumped Warbler parentage. If this were the case I think the white throat and white supercilium most strongly suggests “Myrtle” Yellow-rumped Warbler as one parental species. Other features clearly resemble Townsend’s Warbler although the face pattern is different from that species in my opinion. The almost complete absence of yellow coloration would also need to be explained.
Could this be a hybrid “Myrtle” Yellow-rumped Warbler X Townsend’s Warbler? Many features of the bird fit one or other of this species pair. In some of my photographs it looks like a Myrtle and in others a Townsend’s Warbler! On several occasions it sat around upright on long legs and preened its chest feathers and I thought it looked just like a Yellow-rumped Warbler. The posture in the photograph above looks just like that species and the stoutness of the bill is striking too. Quite unlike the perched horizontal posture and finer more delicate bill of a Townsend’s Warbler. Very baffling!
I would be interested in hearing what other people think about this warbler. Perhaps someone even encountered a similar looking bird before. So far, my searches on the internet have not yielded anything that looks quite like this bird!