Verification of Unusual Sight Record
For Utah

Rec. # 2020-23

Common name:

Parasitic Jaeger

Scientific name: Stercorarius parasiticus
Date: 22 Sep 2007
Time: 12:56
Length of time observed: (unrecorded)
Number: 1
Age: Juvenile
Sex: unknown
Location: Farmington Bay, WMA
County: Davis
Distance to bird: unknown
Optical equipment: Nikon Monarch 10x42 binoculars, Nikon 20x spotting scope
Weather: (unrecorded, not poor)
Light Conditions: (unrecorded, looks overcast in photos)
Description:        Size of bird: Medium-sized jaeger
(Description:)       Basic Shape: Gull shape, like all jaegers
(Description:)  Overall Pattern: Dark morph
(Description:)            Bill Type: Jaeger bill
Field Marks and
Identifying Characteristics:
See Similar Species, below
Song or call & method of delivery: None
Behavior: Loafing on surface of the water
Habitat: Large bay     
Similar species and how
were they eliminated:
There was much debate at the time this bird was observed regarding whether it was a Parasitic or a Pomarine. Having no experience at the time identifying jaegers myself, I relied heavily on the opinion of other experts. Although I have a few documentary digiscoped photos which I will submit with this record, my identification was based largely on better photos taken by other observers of the same bird, and on the opinion of experts in the Frontiers in Field Identification listserv, who were unanimous in agreeing that the bird was a Parasitic Jaeger (at least in the end: some initially argued for Pomarine but later changed their mind). Those opinions were largely based on the excellent photos by Tim Avery which are in this gallery: (Link to Photos)

Reviewing this record more than a decade later, with more field experience and the benefit of hindsight, I still believe it is a Parasitic Jaeger. One of the main concerns at the time with that identification was a subtle "double flash" presented by the pale bases of the primary coverts. This is visible, for example, here: (Link to Photo) This field mark is more typically associated with Pomarine, but can be seen in Parasitic. More importantly, structural marks all indicate Parasitic, including relatively slender structure and especially the smaller bill relative to Pomarine. The tail coverts are very weakly barred, which is a trait of Parasitic more than of Long-tailed or Pomarine, for example: (Link to Photo) The underwing coverts were significantly darker than the flanks, which also indicates Parasitic. The small bill and relatively subtle doub
le-flash are particularly evident here: (Link to Photo) In many views there is no double-flash evident, for example: (Link to Photo)
This view exaggerates the double-flash, but shows well the near lack of barring in the undertail coverts: (Link to Photo)
Previous experience with
this & similar species:
This was the first time I had seen any jaeger. I have since seen dozens of each jaeger species, including Parasitic.
References consulted: Sibley Guide to Birds
Description from: From photo(s) taken at the time of the sighting
Observer: Ryan P. O'Donnell
Observer's address: 106 W Camino Vista, Phoenix, Arizona (currently, at the time I was in Logan, Utah)
Observer's e-mail address: **
Other observers who independently identified this bird: Widely-chased rarity, but I don't know the full list of observers.
Date prepared: 18 Jun 2020
Additional material: Photos
Additional comments: Colby Neuman recently asked me to submit a record of this bird to the UBRC. My eBird list: