28-B-2016 Chestnut-sided Warbler

STATUS
Accepted
DATE VOTING COMPLETED
1ST ROUND
7-0
DATE SIGHTING OCCURRED
DATE REPORT PREPARED
REPORTER
Cheryl Huizinga
OTHER OBSERVERS
None
LOCALITY OF OBSERVATION
Deer Flat NWR Kingfisher Trail, in Canyon Co. Idaho
HABITAT WHERE THE BIRD WAS OBSERVED
Trail that goes along lots of trees, bushes and open grassy areas.
SIGHTING DURATION, CONDITIONS, and EQUIPMENT USED
Warm, sunny morning after an evening of rain and wind. I was using a pair of Zeiss SF 10x42 binoculars.
DID YOU TAKE NOTES?
No, not at all
DID YOU CONSULT A FIELD GUIDE OR OTHER REFERENCE WORK?
Yes, later the same day
WHICH GUIDE(S) OR REFERENCE(S): DID YOU CONSULT?
I looked at Sibley app on my iphone after the sighting to match my observations to a bird, going with those mental notes mentioned above.

Sibley app for iphone. Later when I got home I looked at the Warbler app on my iphone, the Peterson’s Warbler book and at several pictures of the species on the internet.
DESCRIPTION OF THE BIRD(s)
Warbler Family. The first thing I noticed when it popped out in front of me was that the bird was a warbler species because of size and behavior: small active bird foraging through the leaves looking for insects. Then I saw the white eye ring which really stood out (popped) from the gray face and bright golden olive-green top of head and back (other descriptions say lime-green but I thought golden olive-green when I saw it) which told me this was not a warbler I see often. The top of the head was bordered by gray around the face which really made the color of the head and back stand out. I saw 2 lighter wing bars and whitish-light gray underparts. Bill was small and pointed and I didn’t notice much color on it. I did not see any striping along the sides so after looking at the apps noted above, I figured it must be a 1st winter bird.
BEHAVIOR OF THE BIRD(s)
It was in a mixed flock of warblers (Yellow-rumps and Orange-crowned) Warbling Vireos and Black-capped Chickadees – about 20 birds in all. I saw the flock moving loosely my way with the chickadees calling back and forth at a distance so stopped and watched the group foraging and was hoping that the flock would move my way so I could see the flock closer and to hopefully see something different. This particularly bird popped out from a dense shrubby Russian Olive tree about 50 ft. in front of me foraging through the leaves about 3-5 ft. off the ground. It foraged in that bush for about 2 minutes with a Warbling Vireo - coming in and out of view, with me making mental field mark notes about the bird. Then I watched as several of the flock moved on beyond the Russian Olive to another area and I could no longer find the warbler in question. I stayed there for quite a while hoping they would come back to that spot but the flock had moved on to distant trees.
HOW AND WHEN DID YOU POSITIVELY IDENTIFY THE BIRD, AND WHAT CLINCHED THE IDENTIFICATION FOR YOU?
I knew it was a different warbler than the ones I usually see so after the flock moved on, I checked the Sibley app on my phone with the field marks of the bird going through my mind over and over. I didn’t immediately know what it was until I matched the mental notes with the description and drawings in the app. Then I knew what it was and felt confident in posting to IBLE and to Facebook Idaho Birding Page.
HOW DID YOU ELIMINATE SIMILAR SPECIES? WHAT WERE THEY?
The only other warblers that have a white eye ring that pops off a gray face is the 1) Virginia’s and Nashville Warblers both of which I am familiar with. They lack the “lime-green” back and whitish underparts. 2) The Canada Warbler but it has yellow underparts and plain gray back, and 3) the Magnolia Warbler which has yellow underparts and gray back.
WHAT IS YOUR EXPERIENCE WITH THIS (AND SIMILAR) SPECIES?
I have had only 6 other sightings of a Chestnut-sided Warbler – Life sighting was in AZ in 1/2009, one at Foote Park, Ada Co. Idaho in 6/2009, in Maine 7/2009, 2 sightings in TX spring 2010, and in Columbia 2/2016. So definitely not a lot of experience with this species.
DESCRIBE YOUR GENERAL BIRDING EXPERIENCE
Intermediate birder with 14 years’ experience.
ADDITIONAL INFORMATION (If any)
Mentally I was keeping track of the field marks while trying to re-see the bird.

WERE PHOTO(S), VIDEO, AND/OR AUDIO OBTAINED FROM THIS SIGHTING?
None

FIRST ROUND VOTING:

Cliff Weisse
Accept

Description supports the identification of Chestnut-sided Warbler.

Jay Carlisle
Accept

Convincing description of key field marks

Shirley Sturts
Accept

Well described
Similar warblers eliminated

Darren Clark
Accept

Description is good and eliminates similar species.

Dave Trochlell
Accept

The description and timing of occurrence seem correct for a Chestnut-sided Warbler.

Doug Ward
Accept

Decent description of an immature plumaged Fall bird. While a few more notes would have been preferred, most key field marks were mentioned in the report.

Carl Lundblad
Accept

Written description effectively eliminates other candidate species including those in the Leiothlypis, other Setophaga, and yellow Warbler. Only slightly troubled by the "olive-green" description of the mantle/crown, since these are usually quite bright green, but everything else sounds spot-on for Chestnut-sided. It would have been useful if the notes had been recorded prior to consulting references, especially given the observer's relatively low familiarity with this species. However, it sounds like Cheryl was carefully committing field marks to memory at the time of the sighting. Timing is good for Chestnut-sided, and this is one of our more regular "eastern" vagrants.