Sighting Record for Utah

Common name:	Yellow-billed Loon
Scientific name:	[Gavia adamsii]
Date:	19 Nov 2022
Time:	3 PM
Length of time observed:	100 minutes
Number:	1
Age:	Juvenile
Sex:	unknown
Location:	Hyrum reservoir
County:	Cache
Latilong:
Elevation:
Distance to bird:	30 yards to 50 yards for some photos
Optical equipment:	Zeiss Diascope 85, 20-75x eyepiece, Zeiss 8x25 binoculars.
Weather:	Mostly sunny
Light Conditions:	Good light, somewhat backlit at times. The bird was closest toward dusk.
Description: Size of bird:	Larger than Common loons
(Description:) Basic Shape:	Loon shape with large blocky head, thick neck, bill held slightly upward.
(Description:) Overall Pattern:	Buffy barring on the back.
(Description:) Bill Type:	Pale bill, with pale top of culmen.
(Description:) Field Marks and Identifying Characteristics:	Quite large, thick-necked loon with pale yellow bill, tip of bill entirely pale, knob on forehead with blocky head appearance, pale barring on back, bill held at upward angle. In general vicinity of a Common loon at one point, and clearly larger. Two other Common Loons that were more distant looked quite tiny by comparison. Often staying down for 1:20 to 1:29. I timed nine dives accurately, the shortest was 58 sec, the majority were 1:18 to 1:29 sec, several at 1:20 sec, with long up times as well. (see photos)
Song or call & method of delivery:	No calls.
Behavior:	Diving regularly, with surface times around a minute. So somewhat longer times at the surface, and longer dives than most Common loons and other diving birds I've observed recently.
Habitat:
Similar species and how were they eliminated:	Pale culmen, and pale outer half of bill eliminates Common Loon. Straight culmen gives impression of upturned bill. Outer half of bill entirely pale. Obvious pale barring on back. Larger than Common Loons in the vicinity (no side by side comparisons, but one Common Loon was within 50 yards and were clearly smaller, a couple other Common loons were within 100 yards and clearly smaller), thick neck, blocky head, bill held pointed upward. Other loons and grebes are much smaller. Birdsoftheworld.org states "Only characteristic diagnostic in all plumages and ages is color of culmen (ridge of upper mandible). In Common Loon in winter plumage this ridge and about 5 mm on either side is black (in breeding plumage the entire bill is black), but in Yellow-billed Loon at least the distal half and usually distal two-thirds is whitish-yellow".
Previous experience with this & similar species:	Saw the Yellow-billed loon at Willard Bay last fall. I've seen many winter plumage Common loons recently, around 100 this fall.
References consulted:	Sibley app, Sibley v1, v2, Nat Geo 7th ed, Birdsoftheworld.org.
Description from:	From photo(s) taken at the time of the sighting
Observer:	Bill Hunt
Observer's address:	1535 Millcreek Drive, Ogden UT 84404
Observer's e-mail address:	**
Other observers who independently identified this bird:	Bryant Olsen reported the first definite ID on Nov 15, after an early tentative report.
Date prepared:	11/28/2022
Additional material:	Photos
Additional comments:	ebird description written Nov 19. https://ebird.org/checklist/S122694264