Sighting Record for Utah

Common name:	Chestnut-sided Warbler
Scientific name:	Setophaga pensylvanica
Date:	May 28, 2024
Time:	11:38 am
Length of time observed:	1 minute
Number:	1
Age:	adult
Sex:	female
Location:	Devil's Kitchen, Needles District, Canyonlands National Park
County:	San Juan
Latilong:	N 38.136523°, W 109.860066°
Elevation:	5280 ft (exactly mile high!)
Distance to bird:	Observed while sitting at a picnic table ~15 feet from the bird at just above eye level
Optical equipment:	Vortex Razor HD 8x42
Weather:	clear, sunny, light breeze, temps upper 70s
Light Conditions:	indirect lighting (in the shade), but relatively bright from reflected light off rock features
Description: Size of bird:	warbler sized - small, 5 inches
(Description:) Basic Shape:	warbler shaped - shorter/heftier than gnatcatcher but slightly slimmer-build/longer-shaped compared to vireo (e.g., Plumbeous)
(Description:) Overall Pattern:	white underparts with mixed green, yellow, dark tones on uppers
(Description:) Bill Type:	small, thin, straight, pointed, black bill
(Description:) Field Marks and Identifying Characteristics:	A small bird was first noticed by my son, and I promptly got my binoculars on the spot. The bird was mostly hidden at first while it was striking an insect (caterpillar?) against the branch; however, I could at least see that it had mostly white underparts and based on its movements was not likely a gnatcatcher. The bird remained partially hidden for 20 or 30 seconds, and during that time I was guessing it would be a plumbeous vireo based on the behavior, size/shape, and white underparts. Once its meal was consumed, the bird hopped into open view, where I immediately recognized it as a chestnut-sided warbler. The most obvious field marks were the chestnut flanks along clean, white underparts and the characteristic black eyeline-and-malar-stripe on the face with lime-yellow cap. Yellow-white wingbars were also prominent. The bird was viewed in the open for at least 10 seconds and presented a few different angles before it flew around the corner and we lost sight. We walked over to where it had flown and tried to relocate it, including pishing to draw it out, but we were unsuccessful. During the initial viewing, I had been narrating the observations to my son, and as soon as the bird flew away, I said something like "oh wow, I think that is quite rare in Utah and probably the best bird of our trip." After we returned to the picnic table, I looked up CSWA on my Sibley app to confirm that the bird was out of range (Sibley shows CSWA as a regular vagrant to western US) and also the particular plumage of this bird. During the observation, I noted that the chestnut markings were not as extensive as on some birds, nor did the head markings seem as bold or striking as they sometime can be. The Sibley guide confirmed that these attributes are typical of adult females in alternate plumage; all very consistent with the observations.
Song or call & method of delivery:	no vocalizations; bird was silent.
Behavior:	The bird showed typical warbler/vireo behavior, feeding on an insect gleaned from foliage and moving in short hops along the outer parts of mid-level tree branches. This bird perhaps did not show the highest level of energy, with a pace of movement that seemed a bit sluggish, more on par with a vireo's gleaning activity. However, we saw it just as it had captured some prey, and otherwise we did not get to watch it for an extended period of time. Given that it was well out of range and habitat, there could have been some level of exhaustion.
Habitat:	The immediate habitat was a shady, small (~100 sq ft) grove of deciduous trees and shrubs nestled within the fracture zone between large, house-sized boulders. There were similar grove patches nestled within adjacent areas between the Devils Kitchen boulder field that expanded the total habitat space to be 5x this size. Overall, the small deciduous bushes and trees at the site were easily the most appropriate habitat for the CSWA within at least 5 miles (ie., nearest wooded canyon).
Similar species and how were they eliminated:	Other than during initial views while the bird was largely hidden, I did not consider other species after seeing it in the open. The ID seemed 100%. In preparing this report, I did check what would be the most likely confusion, with Sibley suggesting a female bay-breasted warbler given the chestnut coloration along its flanks. However, BBWA would not have had clear, white underparts but rather creamy/buffy tones that extend up to the throat and face; BBWA would also lack the facial markings and light crown. I am also familiar with BBWA and am certain it was not this species.
Previous experience with this & similar species:	I am a life-long eastern-US birder and am very familiar with CSWA as a regular spring and fall migrant and local nester. Have seen many, many times, including several the previous few weeks in Tennessee before going on this trip to Utah.
References consulted:	Sibley Guide to confirm female plumage and to explore potentially similar species.
Description from:	From: Notes made later
Observer:	Steve Goodbred
Observer's address:	9833 Albemarle Lane, Brentwood, Tennessee 37027
Observer's e-mail address:	**
Other observers who independently identified this bird:	My son first noticed the bird, but he is not a birder.
Date prepared:	June 3, 2024
Additional material:
Additional comments:	I first posted this sighting as part of an ebird checklist - https://ebird.org/checklist/S177431062 eBird Regional reviewer Bryant Olsen flagged the sighting as a state review species and asked that I make a full report here. I also have a photo of the specific site that the bird was seen, and I am glad to forward that if it may be of use.