Verification of Unusual Sight Record
For Utah

Rec. # 2017-46a

Common name:

Arctic Tern

Scientific name: Sterna paradisaea
Date: 8-8-17
Time:  ~420pm
Length of time observed:  20 minutes
Number: 1
Age: adult
Sex: unknown
Location: Willard Bay State Park, air boat launch ramp
County: Box Elder
Distance to bird: 20 to 200+ feet
Optical equipment: Swarovski EL 10x42 binoculars
Weather: mostly clear, some breeze
Light Conditions: mostly good, sometimes the bird was backlit but sometimes ideal lighting
Description:        Size of bird: a small-ish tern, slightly smaller than Forster's
(Description:)       Basic Shape: longs wings & tail, small body
(Description:)  Overall Pattern: gray, white, & black
(Description:)            Bill Type: short and pointy
Field Marks and
Identifying Characteristics:
I first noticed a slightly smaller tern (than Forster's) with a noticeably dark belly, a full dark cap, and a relatively dark reddish bill as it flew past and I suspected an adult Common as that would be much more expected. Then I saw a very thin dark trailing edge to the outer primaries and remembered that being a fieldmark for Arctic so I kept watching as it came by every 30-60 seconds. Over the course of 10+ minutes I had enough views to discern a relatively small bill, rounded head, long tail feathers with dark on the outer web, and very contrasty plumage such that a narrow pale cheek separated the black cap from a dark gray belly. I called out to others to take a look and fortunately Sherry had a camera!
(see photos)
Song or call & method of delivery: I heard one soft call while in flight
Behavior: Flying back and forth along water channel in loose company with ~10 Forster's Terns
Habitat: Water channel surrounded by open habitats at edge of Great Salt Lake
Similar species and how
were they eliminated:
Forster's and Common Tern.

Forster's has a lighter orange and larger bill, much paler upperparts, and pale outer webs to tail feathers.

Common is most similar to Arctic but is differentiated especially by having a larger bill and a wider area of black on the primaries. Leg length can be an additional feature (long in Common than Arctic) but - as this bird was in flight for the entirety of the observation - I wasn't able to assess this feature.
Previous experience with
this & similar species:
I have seen at least 50 Arctic Terns - mostly in Alaska and on several pelagic trips but also several individuals in Idaho and Delaware.
References consulted: Mostly Sibley but also the Collins Bird Guide
Description from: From memory
Observer: Jay Carlisle
Observer's address: 4202 N Whitehead Street
Observer's e-mail address: **
Other observers who independently identified this bird: Sherry Liguori (took photos) and several others that were a part of our field trip
Date prepared: 8-11-17
Additional material: Sherry Liguori took several photos at the first sighting
Additional comments: My eBird checklist with photos embedded is here: Bryant Olsen and Matthew Pendleton re-found the bird on the following day and took many photos that are embedded in this eBird checklist: