36-B-2017 Blackpoll Warbler

STATUS
Accepted
DATE VOTING COMPLETED
1ST ROUND
7-0
HOW MANY OBSERVED?
1
DATE SIGHTING OCCURRED
DATE REPORT PREPARED
REPORTER
Heidi Ware
OTHER OBSERVERS
Fellow IBO bander Elizeth Cinto Mejia extracted the bird from the net and IBO volunteer Mike Gindling was there when the bird was banded and took photos. Cheryl Huizinga later re-found the bird free-flying at the site. Denise Hughes and another birder also observed the free flying bird as late as 11:30am the same day.
LOCALITY OF OBSERVATION
The Intermountain Bird Observatory's Boise River Research station, near the intersection of Highway 21 and Warmsprings Ave. lat/lon 43.542181, -116.097247
HABITAT WHERE THE BIRD WAS OBSERVED
Cottonwood forest with mostly willow and currant understory.
SIGHTING DURATION, CONDITIONS, and EQUIPMENT USED
We captured the bird during standardized mist netting at IBO's Boise River station. We caught it at 8:15am and released it at 8:40am after taking photos and measurements. It was later re-found free flying by Cheryl and was seen foraging at the site as late as 11:30am the same day. Weather was clear but a bit smoky, light breeze, probably around 90 degrees by 11am.
DID YOU TAKE NOTES?
Yes, during the observation
DID YOU CONSULT A FIELD GUIDE OR OTHER REFERENCE WORK?
Yes, during the observation
WHICH GUIDE(S) OR REFERENCE(S): DID YOU CONSULT?
I double checked the ID in the Pyle guide to reference age and sex details and used the Sibley guide phone app.

Identification Guide to North American Birds, Part I: Columbidae to Ploceidae 1997 by Peter Pyle
DESCRIPTION OF THE BIRD(s)
See photos for more details.

It was a hatch-year Blackpoll Warbler in formative plumage.

This warbler was overall yellow on the head and chest (a few smudgy chest streaks), with a darker gray/greenish back (a few streaks), white belly, and white undertail coverts. It had white windows on the outer tail feathers. Very long undertail coverts reaching almost to the tip of the tail feathers. Two white wing bars. It was much more bulky feeling overall than other warblers we regularly band such as Yellow-rumped and Yellow. It had a slight eyeline. Bill was blunt, more like a MacGillivray's Warbler bill. Wing chord of 75, tail length 51. Bird was very lean with only moderate muscle. It was a Hatch-Year bird with incomplete skull ossification. Pyle gave details about sexing hatch-year birds based on back streaking and other characteristics but said many individuals should be listed as sex unknown.
BEHAVIOR OF THE BIRD(s)
I saw the bird only in-hand. In-hand it called a few times with a distinctive sharp chip note. I was told by the birders who watched it that it foraged low to the ground (mostly below chest height) and was also seen on the ground.
HOW AND WHEN DID YOU POSITIVELY IDENTIFY THE BIRD, AND WHAT CLINCHED THE IDENTIFICATION FOR YOU?
As we took the bird out of the net, we knew we had something extremely rare because it was so different from our regularly expected species. As soon as I saw the overall yellow color, dark back, and white in the tail feathers I knew it was rare. Eli was extracting the bird and I asked her if it had orange legs. When she said yes, I thought it must be a Blackpoll Warbler. Back at the banding station I called Jay Carlisle to make sure there were no other similar species I should consider (and to rub it in a little bit!), and then checked Pyle and Sibley to rule out Bay-breasted Warbler. I used Pyle to confirm that I should list it as sex unknown.
HOW DID YOU ELIMINATE SIMILAR SPECIES? WHAT WERE THEY?
First winter female Bay-breasted Warblers are similar. However, they have buffy undertail coverts that are shorter than Blackpoll. Bay-breasted would also have gray legs, an unstreaked chest, and a lighter back
WHAT IS YOUR EXPERIENCE WITH THIS (AND SIMILAR) SPECIES?
I've seen one other Blackpoll Warbler and a few Bay-breasted Warblers. Both on their wintering grounds. I have banded thousands of other warblers, mostly of Idaho's expected suite of warbler species. I have experience identifying vagrant and unexpected species in the hand over 10 seasons working with the Intermountain Bird Observatory.
DESCRIBE YOUR GENERAL BIRDING EXPERIENCE
I have been seriously birding in the US and Latin America, as well as Africa, since 2008.
WERE PHOTO(S), VIDEO, AND/OR AUDIO OBTAINED FROM THIS SIGHTING?
Photo
SUPPORTING IMAGES

FIRST ROUND VOTING:

Shirley Sturts
Accept

Photos and description confirm the Identification

Dave Trochlell
Accept

This was a totally convincing report.

Darren Clark
Accept

Photo and description are good.

Doug Ward
Accept

Excellent description with diagnostic photos – helps to have the bird in hand. Hope Jay’s nose has healed.