Sighting Record for Utah

Common name:	Philadelphia Vireo
Scientific name:	Vireo philadelphicus
Date:	August 22, 2018
Time:	1:45 pm
Length of time observed:	10 minutes
Number:	1
Age:	Adult
Sex:
Location:	Tonaquint Nature Center
County:	Washington
Latilong:
Elevation:
Distance to bird:	15 feet
Optical equipment:	10X42 Nikon Monarchs
Weather:	Somewhat overcast. A large storm persisted through the night and had just finished dumping rain when I arrived. Temperature remained cool and bird activity was high.
Light Conditions:	Clear, crisp lighting. After the storm passed the clouds opened up providing direct sunlight.
Description: Size of bird:	Small passerine. 5-6 inches in length
(Description:) Basic Shape:	Thicker build than a parulidae warbler, but roughly the same size.
(Description:) Overall Pattern:	Brownish-gray back and yellow breast and throat. Dark cap and white supercilium.
(Description:) Bill Type:	Typical vireo bill. The bill was shorter and more compact than a typical WAVI, but more slender than Plumbeous and Cassin's Vireos.
(Description:) Field Marks and Identifying Characteristics:	The vireo I observed appeared very yellow (even to the naked eye) and showed significant contrast in the face, more so than I would expect to see in even the brightest of Warbling Vireos. The color of the bird was the first thing I noticed when I initially saw the it. I was standing on the bank of the river when it flew overhead from dense vegetation to a thick stand of trees and shrubs to the west. My first thought was that it was a warbler of some sort, but as it it got closer in flight I noticed a thicker vireo-like bill and stockier body shape -- unlike a warbler, which would be more slender in both regards. I walked to the stand of trees and re-found the bird within a couple of minutes. It was very active in dense foliage and remained difficult to see . Before I completely lost track of it I was able to get 5 clear looks through my binoculars; the longest length of observation being about 10 seconds. Overall color/contrast: The bird had a dusky-gray crown and gray cheeks which contrasted with a bold white supercilium and white crescent, visible underneath the eye. Most notably, the vireo had a yellow wash on the throat. This was the most convincing characteristic that I observed in the field. The yellow extended from the throat, down the breast and into the flanks. The back appeared to be a brownish-gray color and the primaries and secondaries of the wings were a yellowish-green. Bill Size/Shape: The bill appeared to be shorter and more compact than a typical Warbling Vireo, but more slender than a Plumbeous or Cassin's. However, it's hard to judge without a direct comparison, but that was the impression I got after encountering 4-5 WAVI earlier that afternoon. Body Shape: Thicker build than a parulidae warbler, but roughly the same size: small passerine about 5-6 inches in length. The PHVI had a very similar body shape to a WAVI, ruling out the stockier solitary vireos. The head was relatively flat giving it a "long-looking" appearance.
Song or call & method of delivery:	Silent
Behavior:	Flitting around actively through thick foliage at all levels of the canopy. Hardly stayed in one place for more than a few seconds.
Habitat:	Relatively open area near the Virgin River at the northeast corner of Tonaquint Nature Center. Observed the bird fly from vegetation in the river to a relatively small, but dense stand of trees next to the riverside trail.
Similar species and how were they eliminated:	I've encountered Philadelphia Vireos once before in Utah and numerous times in the east -- Minnesota, New Hampshire, Virginia, etc.. Having lived in Utah for the majority of my life, I've become very familiar with Warbling Vireos. After countless observations I have developed a strong understanding of the species: its behavior, song, and physical characteristics. With that being said, I've seen them exhibiting various degrees of brightness and feel quite comfortable in my understanding of the scope of color contrast in WAVI populations. The vireo I observed appeared very yellow, even to the naked eye when first seen in flight. When viewed through binoculars while perched, I was able to get clear looks at the bird from several different angles. Warbling Vireo: The bird had a dark gray crown and cheeks in contrast with a bold white supercilium and white crescent visible underneath the eye. Most notably, the vireo had a yellow wash on the throat, unlike a brightly-colored WAVI. This was the most convincing field mark I observed. The yellow extended from the throat, down the breast and into the flanks. The back appeared to be a brownish-gray color and the primaries and secondaries of the wings were a yellowish-green. I would expect a typical Warbling Vireo to have a warm-brown coloration on the back and wings. Brighter WAVI individuals can have yellow-green coloring there, but its usually faint and not as rich. Some WAVI have a yellow wash on the breast, but never brightly on the throat. The bill seemed shorter and more compact than a WAVI. However, it's hard to judge without a direct comparison, but that was the impression I got after encountering 4-5 WAVI earlier that afternoon The bill was also a uniform gray. To my memory, most, if not all of the Warbling Vireos that I have been seeing at this time have had bi-colored bills -- a pale base with a dark tip. However, I'm unsure if this is a reliable field mark. Cassin's/Plumbeous Vireos: Shape: Solitary vireos appear much stockier than the more slender build of the Philadelphia Vireo. The head is also more rounded, while the vireo I observed had a flatter head, giving it a long-looking appearance (compared to solitary vireo sp.). Coloration: Plumbeous Vireos lack any yellow and are lead-gray and white. Cassin's Vireos however have a similar color scheme, but still lack yellow on the throat. Also, most of the yellow on the Cassin's is concentrated on the flanks. The wings are also typically more yellowish-green depending on the brightness of the individual. Both Cassin's and Plumbeous Vireos have white "spectacles" unlike this bird which had an eyebrow that extended well past the back of the eye. There was no complete white border around the eye either connecting the white crescent underneath.
Previous experience with this & similar species:	(See above)
References consulted:	Sibley Guide to Birds (App on iPhone)
Description from:	Notes made later
Observer:	Kendall Watkins
Observer's address:	325 N Red Stone Rd Washington, Utah
Observer's e-mail address:	**
Other observers who independently identified this bird:
Date prepared:	September 9, 2018
Additional material:
Additional comments:	Used notes taken same day of sighting, but not while observing the bird. No photos. WAVI - Warbling Vireo PHVI - Philadelphia Vireo