Verification of Unusual Sight Record
For Utah

Rec. # 2017-46

Common name:

Arctic Tern

Scientific name: Sterna paradisaea
Date: 8/9/2017
Time: 6:00pm
Length of time observed: 45 minutes
Number: 1
Age: adult
Sex: ?
Location: Willard Bay State Park, air boat launch ramp
County: Box Elder
Elevation: 4212
Distance to bird: Less than 3m at closest apprach
Optical equipment: Nikon 10x50 Binoculars
Weather: Mostly cloudy
Light Conditions: Dim lighting and somtimes backlist
Description:        Size of bird: 12in long
(Description:)       Basic Shape: Typical tern
(Description:)  Overall Pattern: Overall dark gray
(Description:)            Bill Type: short,all red
Field Marks and
Identifying Characteristics:
Adult in breeding plumage, very dark gray breast with contrasting white throat, short all red bill, short tail with dark outer edge, pale gray translucent primaries with dark edges.High contrast white rump against gray back.
(see photos)
Song or call & method of delivery: Heard it kip a few times, very different from Forster's calls, weaker and not as harsh.
Behavior: Flying up and down a canal in a circuit, often just feet above our heads.
Habitat: Freshwater canal at outflow or Willard Bay, near huge marsh complex of Bear River Migratory Bird Refugee
Similar species and how
were they eliminated:
Forster's Tern-all white breast, longer orange bill with black tip, longer tail with white outer edge. Low contrast between back and rump.

Common Tern-Similar, but have longer bill with black tip, longer tail, less contrast between rump and back, but most importantly, adults should have very dark primaries, above and below, forming a dark wedge on the wing tips. These primaries are never translucent or have white inner webbing. Also breast is not as dark a shade of gray.

Additionally most adult Forster's and Common Terns should be beginning to molting out of breeding plumage, Arctic Terns molt later. This tern was in full breeding plumage, no sign of molting.
Previous experience with
this & similar species:
 I've had a few possible Arctic Terns before, but never an adult in breeding plumage. I've seen many Common and Forster's Terns
References consulted:  I've actually been doing a lot of research on this species lately, consulting Birds of North America online and the Macaually Library studying age and molt patterns. Ironic this bird showed as I was doing my research.
Description from: From photo(s) taken at the time of the sighting
Observer: Bryant Olsen
Observer's address: 84102,SLC,UT
Observer's e-mail address: **
Other observers who independently identified this bird: Matt Pendleton and Lauri Taylor were with me, reported the day earlier by Jay Carlisle.
Date prepared: 8/9/17
Additional material: Photos
Additional comments:  eBird checklist: