Verification of Unusual Sight Record
For Utah

Rec. # 2005-

Common name:

Mourning Warbler

Scientific name: Oporornis philadelphia
Date: 9-01-05
Time: 10:00 a.m.
Length of time observed: 20 minutes
Number: 1
Age: juvenile
Sex: undetermined
Location: Scott M. Matheson Wetlands Preserve
County: Grand
Latilong: W 109 31, N 39 59
Elevation: 4000 ft
Distance to bird: in the hand
Optical equipment: none
Weather: clear
Light Conditions: sunny
Description:        Size of bird: bird in hand matches measurements for species
(Description:)       Basic Shape: bird in hand conforms to species
(Description:)  Overall Pattern: buffy-olive-yellow
(Description:)            Bill Type: straight, pointed, pink lower mandible
Field Marks and
Identifying Characteristics:
narrow broken eye ring, more pronounced on lower lid; pinkish lower mandible; dusky lores to cheek patch; bright yellow throat; yellow breast; buffy-olive flanks; indistinct buffy-olive patches on sides of neck, coming part way onto sides of breast; pink legs; long undertail coverts
(see photos)
Song or call & method of delivery: didn't hear vocalization
Behavior: this bird was trapped in a mist net so didn't observe its normal behavior
Habitat: willows in dense brush near junction of Colorado River and Mill Creek (location of mist net)
Similar species and how
were they eliminated:
Our team is familiar with, and has banded, the following birds and has eliminated them for the following reasons:

Orange-crowned Warbler – we banded 42 of these birds during this fall’s migration (juvenile as well as adult birds) and could say our bird was much larger. In addition, leg and beak color are different and there was no body streaking on our bird.

Nashville & Virginia’s Warblers – our bird was much larger, had an incomplete eye-ring as opposed to complete eye-ring, had a pink lower mandible and pink legs, which these birds do not have.

Common Yellowthroat – again, our bird was much larger. Immature Yellowthroat doesn’t have a yellow throat or lower pink mandible.

Yellow Warbler – smaller than our warbler, immature YW doesn’t have a bright yellow throat, or lower pink mandible.

MacGillivray’s Warbler – we have handled several MacG and at first glance, we thought this was what we had based on general color, size and broken eye ring. We knew we had a hatch year bird based on the plumage. After further examination, we noted a definite bright yellow throat on
this bird, as opposed to the whitish throat of a hatch year MacG, and a yellow breast (see photos). We also noted the bird didn’t have a complete “hood” but did have some olive markings (similar in color to the flanks) from the nape onto the sides of the breast, but not meeting across the breast. Also, under tail coverts seemed long. The bird had a “dusky” cheek patch. Other similarities included a pink lower mandible and pink legs and feet. The wing chord measurement for this bird is 55 mm, with a weight of 9.7 g. There was only a trace of fat on the bird. We then referenced Sibley’s Western Field Guide, National Geographic’s Field Guide to Birds of NA, and finally, Pyle’s Identification!Guide to NA Birds (this is the major reference we use when banding birds). Pyle gives a wing chord range for the Mourning Warbler of 54-63
mm (juvenile female) and 57-65 mm (juvenile male) and for the MacG of 52-61 mm (juvenile female) and 54-64 mm (juvenile male), so there is an overlap with these species. The tail measurement for this bird is 50 mm, which fits within the ranges for a juvenile MacG, Mourning and Connecticut. The appearance of tail length seems to be with the length of the undertail coverts. Weights of the adult MacG we banded that day were 12.3 g and 11.4 g. and wing chords were 58 mm and 60 mm respectively. There was a trace of fat on the first MacG and none on the second.

Connecticut Warbler – None of the team is familiar with this warbler. Realizing the strong similarities between it and the Mourning Warbler, we compared the wing chord measurement of our bird to those given for the CW in Pyle. These measurements (63-73 mm for juvenile female and 65-75 mm for juvenile male) indicate that our bird is smaller than the CW. Also, Pyle’s description of the eye ring for a juvenile male or female says it is a complete eye-ring, as opposed to the incomplete eye-ring of our bird. Pyle doesn’t give a weight range, but referencing Sibley’s gives us a general weight of 15 g for the CW and 12.5 g for the MW. Sibley’s also makes note of the difference in undertail coverts with the CW’s being much longer, giving a short-tailed appearance. Looking at two of the submitted photos, it is apparent that the undertail coverts
are long but not reaching near the tip. Sibley makes note that they are longer than the MacG but shorter than the CW.
Previous experience with
this & similar species:
See similar species and how they were eliminated
References consulted: Identification Guide to North American Birds, Part 1, by Peter Pyle; The Sibley Field Guide to Birds of Western North America, by David Allen Sibley; National Geographic Society's Field Guide to the Birds of North America
Description from: Notes taken at time of sighting
Observer: Marian Eason
Observer's address: 698 West 400 North; Moab, UT 84532
Observer's e-mail address:
Other observers who independently identified this bird: There were three of us who actually handled the bird in an effort to identify it: Bob Bailey, Marcy Hafner, Marian Eason
Date prepared: 11-4-05
Additional material: Photos
Additional comments: Information prepared sooner than today but we were waiting for confirmation of measurements. Photos being sent to the Utah Bird Records Committee