Kas Dumeroese arrived and saw it within 10 minutes of my discovery and Ben Bright saw it an hour later.
LOCALITY OF OBSERVATION
University of Idaho Main Campus
HABITAT WHERE THE BIRD WAS OBSERVED
Parking Lot! 2 rows of ornamental ash trees run through the center of the parking lot, and the warbler flock was feasting on smoky-winged ash aphids. Paradise creek runs adjacent to the parking lot, with dogwoods, willows, and spruces, but the birds were mostly using the 2 ash rows.
SIGHTING DURATION, CONDITIONS, and EQUIPMENT USED
Relocated several times (maybe 5 total encounters) over 2 hours, but each viewing lasted only ~10-30 seconds. Light was decent, but it was mostly cloudy to overcast, moist, and cool. It was easy to simply walk west of the 2 ash rows and scan the warbler flocks with the sun at your back. At one point I lent Kas my binoculars, and could easily pick out and ID (once I knew it was present) the bird with my naked eyes (on account of the slightly smaller size and tail-pumping behavior. Otherwise, viewed through Bushnell Elite 10 X 43 binoculars.
DID YOU TAKE NOTES?
Yes, later the same day
DID YOU CONSULT A FIELD GUIDE OR OTHER REFERENCE WORK?
No, not at all
DESCRIPTION OF THE BIRD(s)
Verbatim notes recorded in eBird on 6 Oct. 2016:
As sorting through the YRWA, my eye suddenly was drawn to a slightly smaller drab warbler pumping its tail quite rapidly- a faster and more fluid motion than Northern Waterthrush, for comparison. Next I saw the bright yellow undertail coverts and I knew I had a Palm Warbler. The rest of the body was mostly drab brown except for bold supercillia, pale crescents below eyes, and dark loral lines extending through and behind the eye. Slight blurry streaks on underparts, maybe concentrated on flanks. Usually silent but called a few times- mostly in flight; a much harder/sharper call than the YRWAs, more similar to the metallic chink of Orange-crowned but not as weak.
BEHAVIOR OF THE BIRD(s)
Foraging with YRWA flock and feasting on major flight of smoky-winged ash aphids, but very difficult to watch and follow. Frequently turning up in different parts of the 2 north-south ash rows and maybe once flying to the row of red leaved trees (maples?) further east. I suspect the larger yellow-rumps kept it often on the move, though I'm not sure I ever saw an actual chase. The tail-pumping behavior was so distinctive that the bird could easily be located with the naked eye (and that seemed to work better than sorting through the YRWA with binocs).
HOW AND WHEN DID YOU POSITIVELY IDENTIFY THE BIRD, AND WHAT CLINCHED THE IDENTIFICATION FOR YOU?
Detailed above. As soon as I saw the tail-pumping and yellow undertail, I knew what it was. The face pattern confirmed.
HOW DID YOU ELIMINATE SIMILAR SPECIES? WHAT WERE THEY?
Browner than orange-crowned warbler (except the highly-contrasting bright yellow undertail) and with a bolder face pattern, bold supercillium, and darker eyeline. Different behavior. Ditto Yellow Warbler
WHAT IS YOUR EXPERIENCE WITH THIS (AND SIMILAR) SPECIES?
I've seen palm warblers in Belize and vagrants in New Mexico, Nevada, and Arizona.
DESCRIBE YOUR GENERAL BIRDING EXPERIENCE
Advanced near-daily birder of 15+ years, PhD student studying avian ecology, and member of the Nevada Bird Records Committee.
ADDITIONAL INFORMATION (If any)
[Report prepared on Oct 8] based on notes taken about an hour after the last sighting on Oct. 6
WERE PHOTO(S), VIDEO, AND/OR AUDIO OBTAINED FROM THIS SIGHTING?
FIRST ROUND VOTING:
Description and photos support the identification of Palm Warbler.
Description and photos are convincing
I agree that this was a Palm Warbler.
well described and diagnostic pics
Photo and description are good for Palm Warbler
Good description of both behavior and key marks for this species. Attached photos, while not stellar, did show key marks and distinctive posture and structure.