Verification of Unusual Sight Record
For Utah

Rec. # 2017-36

Common name:

Vaux's Swift

Scientific name: Chaetura vauxi
Date: 7 May 2017
Time: 5:58 pm
Length of time observed: saw it for at least 2 minutes
Number: 1
Age: adult
Sex: unknown
Location: Above nature center pond in Tonaquint Park, St. George.
County: Washington
Latilong: 37.080433, -113.600202
Elevation: ca. 2580 feet
Distance to bird: 80-100 feet at closest approach.
Optical equipment: Leica 10x42 BN binoculars and Nikon D7200 camera (through which I spent a lot of time looking as I snapped photos)
Weather: Pleasant. Ptly cloudy.
Light Conditions: Diffuse, bright light. Sun was low in the sky and mostly behind/left of us. Because the bird was high above us, it was more backlit and thus silhouetted than would be ideal.
Description:        Size of bird: A bit smaller than surrounding swallows.
(Description:)       Basic Shape: Classic swift shape: chubby cigar/spliff with scimitar-shaped wings
(Description:)  Overall Pattern: Brownish, with paler throat area
(Description:)            Bill Type: Not noticeable because it extended so little from face.
Field Marks and
Identifying Characteristics:
Flying with swallows over pond, fairly high (80-300 feet).
-- distinct fluttery swift flight (burst of fluttery flapping punctuated by fast gliding)
-- long scimitar-shaped wings
-- short body and tail (which it often spread in a round fan)
-- hair-like extensions to tail feathers visible in flight & photos
-- all dark with slightly but noticeably paler throat area (fading to background dark by belly)
-- rump noticeably paler
-- silent the entire time it was flying (near as we could detect)
(see photos)
Song or call & method of delivery: none noted (but there was a lot of chatter from the swarm of swallows to mask a call)
Behavior: Distinct fluttery swift flight (burst of fluttery flapping punctuated by fast gliding) in a large mixed flock of swallows over a pond. Never landed.
Habitat: Over a pond surrounded by trees/bushes in a park near a cemetery, riparian strip, and golf course.
Similar species and how
were they eliminated:
I'll restrict my attempts to differentiate this species from other swift species to the swifts regularly found in North America. In truth, there are many swifts around the world which look similar to this species.

1) Black swift: Black swifts are much larger, with longer torsos and slightly forked tails (lacking the Chaetura spines on the tail feather tips).
2) White-throated swift: Though most common in Utah, these swifts are not really similar at all to a Chaetura swift. They have distinct white patches on the undersides and sides of the rump. (There were two White-throated swifts present in the park, though not while the Vaux's swift was visible)
3) Chimney swift: Vaux's swifts are difficult to differentiate from a Chimney swifts. Many of the classic field mark differences are very light-dependent (see my note under Additional Comments below). I cannot prove it wasn't a Chimney swift. However, I believe this was a Vaux's swift because:
-- it is the most likely of the Chaetura swifts in our state,
-- the paleness on the throat was fairly extensive and noticeable,
-- the pale rump was also noticeable and contrasting to rest of upperparts, and
-- the wings seem fairly broad and rounded (though that is admittedly very subtle, I think it is supported by the photos).
One field mark that argues against my ID is that the bird fanned its tail on multiple occasions, which is more suggestive of a Chimney swift, though both species can do that. [By the way, feel free to make my day by talking me into that latter ID.]
Previous experience with
this & similar species:
According to eBird, I've seen this species 53 times since 1996, in North & Central America. That surprises me.
References consulted: Shortly after seeing this bird, Peter & I consulted the National Geographic and Sibley guides. Since then, I've also consulted the Chantler & Driessens's Swift guide
Description from: Notes taken at the time of the sighting
Observer: David Wheeler
Observer's address: 22196 South 1000 East, Salt Lake City, UT
Observer's e-mail address: **
Other observers who independently identified this bird: Peter Wheeler (though note that Peter is a nascent birder with little experience in swifts--his ID was based mostly on my photos).
Date prepared: 29 May 2017
Additional material: Photos
Additional comments: I will send select photos later this week. Unfortunately, the photos are very backlit so the bird appears darker than it did in real life.