Sighting Record for Utah

Common name:	Parasitic Jaeger
Scientific name:	Stercorarius parasiticus
Date:	10-25-25
Time:	10:00
Length of time observed:	~2 hours
Number:	1
Age:	Adult
Sex:
Location:	Willard Bay Reservoir
County:	Box Elder
Latilong:	41.360094, -112.102280
Elevation:	4200 ft.
Distance to bird:	Initially 800 yards and as close as 500? Hard to estimate distance on the reservoir
Optical equipment:	Kowa TSN 883 Spotting Scope
Weather:	mid-60's overcast
Light Conditions:	Good
Description: Size of bird:	~16-18 inches, Ring-billed Gull sized
(Description:) Basic Shape:	Gull like
(Description:) Overall Pattern:	Dark Brown, White
(Description:) Bill Type:
(Description:) Field Marks and Identifying Characteristics:	I first observed a very distant jaeger sitting on the water from the south dike at Willard Bay Reservoir. I could tell that it was an adult light morph, with a chocolatey brown back and white nape, white underside and a dark cap. I told my dad Mike and Esther that I had an adult light morph jaeger and they needed to get on the bird. Both of them rushed down to the car below the dike to grab their cameras, and as I was trying to get Esther's scope on the bird it took off and chased a big group of Bonaparte's and Ring-billed Gulls. I lost it in the swarm of gulls but knew it headed a bit east. We decided to go to the South Marina as that was where the most gulls were on the reservoir and to try to refind the jaeger and get closer to get an ID. Once we got to the South Marina on the dike, we were able to find the jaeger fairly quickly in all three of our scopes. It was still fairly distant (maybe 600+ yards) but luckily we stayed on it for over an hour, watching it preen, periodically get up and chase Ring-billed Gulls, and then loaf again on the water. About 30 minutes into our observation it finally came close enough (~500 yards or so) that we got good looks at the white primary shafts (single flash) that was visible on both the top and bottom sides of the wing. It also splayed its tail out both while preening and while chasing gulls multiple times, and two pointed tail plumes were clearly visible. The pointed tail plumes were somewhere between 1/3 and 1/2 longer than the other tail feathers. It had a dark collar that was pretty much complete but faded towards the center of the breast, and light brown undertail. The bill was completely dark, and the dark cap basically ended in line with the bill with no contrast in color with the base of the bill. Sometimes it would fly straight a couple hundred yards low over the water. Very direct, fast falcon like flight style and it was slender-bodied. It was basically the same size, maybe a tiny bit smaller than the RBGU's it was chasing. Difficult to see but in our photos and video, you can see the primary flashes, and Esther's first picture you can barely see the two pointed tail plumes. (see photos and Video on eBird Checklist)
Song or call & method of delivery:	None
Behavior:	Doing Jaeger things, chasing/harrassing gulls, loafing on the water and periodically preening.
Habitat:	Large freshwater reservoir
Similar species and how were they eliminated:	Long-tailed Jaeger - Lack the primary crescents/flashes of our bird which was visible on a good number of the primaries (at least 5 if not more, but hard to tell at the distance we were viewing it). Primary flash was visible on both top and bottom of the wing LTJA's usually lack the collar that our bird showed. They also usually have a darker cap that contrasts with a lighter colored back of the bird, where ours the cap was basically the same color as the back. They also have a more floating, buoyant flight style. Pomarine Jaeger - Dark cap extends below the base of the bill, and usually contrasts with the lighter-colored base of the bill. Our bird had a completely dark bill and the dark cap ended in line with it. Usually show a double-flash on underwing rather than a single. Tail plumes, even if molting or without spoons, would be blunt rather than pointed like our bird. Much more pot-bellied, bulkier bodied bird.
Previous experience with this & similar species:	This would be the fourth PAJA for me in Utah, I've seen quite a few on annual pelagics of the West Coast. I've seen quite a few Pomarine and LTJA on those pelagics and a couple of each in Utah, but all juvenile birds.
References consulted:
Description from:	Notes taken at the time of the sighting From photo(s) taken at the time of the sighting
Observer:	Max Malmquist
Observer's address:	2377 East Boyes Street
Observer's e-mail address:	**
Other observers who independently identified this bird:	Mike Malmquist and Esther Sumner
Date prepared:	11-3-25
Additional material:	Photos, Video on eBird Checklist
Additional comments:	https://ebird.org/checklist/S281311594