I was scouring the flowering eucalyptus nearer the parking lot when Gary Deghi rescued me and indicated that he had the bird. We chased it for a few minutes around the flowering eucalyptus tree until we finally got very nice looks. The bird was observed by Gary and me for close to a minute at eye-level in light shade, i.e. nearly perfect light.
Overall jizz was similar to a slightly chunkier Yellow-rumped Warbler. The head was pale brownish grey with a faint eyeline mostly in front of the eye breaking an equally indistinct eye ring and a poorly marked malar area. The bill was noticeably long and pointed and the back was pale green with faint streaking on it. The color of the rump was yellowish-green or greenish-yellow depending on which observer was looking at it, and the color of the rump extended well up the back, much further than it would on a Yellow-rumped Warbler. The tail seemed relatively short and upper tail was dark.
The underparts were pale other than indistinct streaking along the sides of the breast extending about to mid flank. The streaking formed a distinct vee from the pattern of the streaking and the otherwise unmarked under parts. The under tail pattern was not observed though it should have been. The vent area showed a pale yellow wash. The wings were dark with two indistinct wing bars and the remiges on the folded wing were conspicuously edged green. Leg color was also not observed and for no good reason.
Identification is rather straight-forward, surprisingly. For regularly-occurring wood warblers with yellow rumps, Magnolia Warbler would show no eye line, distinct blackish streaking if streaked at all, entirely yellow underparts and a complete white eye ring. Yellow-rumped Warbler would not show a distinct vee pattern on the underpart streaking, yellow rump strictly confined to the rump area and would not show green edging on the remiges. Blackpoll Warbler lacks a yellow rump, has a conspicuous wing bars and is not likely to be confused with a Yellow-rumped Warbler. So, we’re left with only CAPE MAY WARBLER, the only warbler with a combination of a long-bill, vee-shaped streaking on the breast, contrasting rump path and greenish edges to remiges. While it seems likely that this was a HY bird, sexing the bird seems problematic.