Idaho Bird Records Committee Rarities Report Form

Species: Glaucous-winged Gull

Reporter: Cliff Weisse, 4125 Beaver Springs Rd., Island Park, ID 83429, 208-558-7789, cliffandlisa@octobersetters.com

Other Observers: None at time of sighting.  I believe this is the same individual previously reported at this location by Jay Carlisle and others on Dec. 23, 2006, IBRC #6-B-07, and also photographed below CJ Strike Dam on 2/21/2007 by Larry Ridenour.

Date of Observation: 2/18/2007

Date Report Prepared: 2/24/2007

Locality of Observation: CJ Strike Reservoir, Bruneau Arm between Upper end near Jack’s Creek and Cottonwood access.  I believe this is the same individual previously reported at this location by Jay Carlisle and others on Dec. 23, 2006, and also photographed on 2/21/2007 by Larry Ridenour, IBRC #6-B-07. 

Habitat: Reservoir with small mud islands

Conditions: Windy and cloudy, winds probably in excess of 30 mph at times making scope views difficult.  I had to set up on the downwind side of my truck.  Binocs used are Nikon Premier 10 x 42, scope Swarovski 80 mm HD w/20-60x eyepiece.  Distance ranged from 30 yards to over 200 yards in flight, estimated 150 yards when perched, possibly farther.  Duration of observation about 20 minutes, then 5 minutes at another location for a total of 25 minutes. 

Did you take notes…  no

Did you consult a field guide or other reference work? Yes, Olsen and Larsson, Gulls of North America, Europe, and Asia.

Description: First winter large gull, overall brownish with no adult gray mantle feathers present.  In direct comparison this individual was clearly larger than 7 Herring Gulls that were present and in close proximity for some of the observation time and approximately the same size as, or possibly slightly larger than, a juvenile Glaucous Gull it was associating with.  Overall appearance was of a light brown bird showing no contrast between any feather tracts.  In flight it looked pale enough at a distance to suggest Glaucous Gull without optical aid.  It had a deep chest and bulky, pot-bellied appearance to the body that was obvious while perched and in flight.  The head was rounded with no noticeable peak at fore crown or hind crown, or not squared off as in typical Herring Gull.  Primary projection was short with only two primary tips visible beyond the end of the tail on the perched bird.  Primaries were wide. 

-Bill was entirely black all the way to the base.  It was heavy, or deep, with strong gonydeal protrusion and more gradual slope to tip of culmen than nearby Herring Gulls.  In direct comparison with Herring Gulls the bill was obviously deeper with much more obvious gonydeal protrusion. 

-Head was brown with face darker than surrounding nape and side of neck but not contrasting nearly as much of as solidly brown as in Western Gull.   Iris was dark.

-Tail was completely brown without any noticeable barring.  Barring was specifically looked for in flight and not seen.

- Mantle overall mottled brown but exact pattern of mantle and scapulars was not noted. 

-Tertials brown with pale tips

-Wing coverts brown with limited pale markings.  Greater coverts with fine pale spotting on distal 1/3 of feathers, solid brown on basal 2/3. 

-Primaries brown with extensive pale tips extending up sides (edges) of feathers.  In flight outer webs were noticeably darker than inner webs but overall primaries appeared concolor with rest of upper wing.  From below in flight the primaries appeared silvery with dusky trailing edge. 

The following is a transcript of an email I sent with comments on the photos taken 2/21 below CJ Strike Dam by Ridenhour, presumably of the same bird. 

“It's a very large Glaucous-winged with very heavy bill, probably a male.  This bird was similar in size to, and may have been slightly larger than, the Glaucous it was associating with when I saw it.  The Glaucous was kind of small for the species but this Glaucous-winged struck me as being very large even when seen flying alone.  The all black bill this late in winter is a Glaucous-winged trait and would be unusual for other large gull species.  The wings, tail and body all appear about the same shade of brown, another Glaucous-winged trait.  Other features that, in my opinion, confirm the ID are:

-The darker brown on the outer wings is confined to the outer webs of the individual feathers
-The bill is fairly long and very heavy for the length with obvious gonydeal protrusion on the lower bill and long, gentle downward curve at the tip of the upper bill.
-Solid dark tertials with limited pale tips
-Primaries with extensive pale edges to the tips of the feathers visible in the flight shots
-Solid brown, not blackish, tail all the way to the base
-Wing coverts kind of plain with limited fine pale markings, not the larger more contrasting pale markings typical of Herring, Thayer's and others.
-Round head with small eye and diffuse darker face contrasting with paler nape/neck/crown
-Dark pinkish legs
-Deep chested and heavy bodied look with proportionately small head

The only thing that's a little "off" for Glaucous-winged is the eye placement.  It looks like it's set somewhat forward, more like Herring Gull, rather than being centered on the face.  In light of the fact that the rest of the bird looks pretty much typical for Glaucous-winged the eye placement doesn't bother me.  The bird also appears somewhat darker in these photos than I remember it looking in the field.  In flight at a distance it didn't appear that much darker than the first winter Glaucous it was with.  It was darker but looked more buffy tan than brown in flight, and light brown when perched.” 

Subsequent research showed that the eye placement is well within normal range for Glaucous-winged Gull.

Behavior: When first observed where the road first meets the reservoir at Jack’s Creek WMA the bird was in flight at a distance of about 150 yards.  It landed on the water several times for short periods and gradually worked its way closer to me.  It flew past at only 30 yards offering excellent views.  It then continued east towards the upper end of Bruneau arm.  I drove to the end of the road and had the bird in view for approximately 20 minutes perched on a mud island and picking at something in the water.  Several times it chased Herring Gulls, also first winter birds, away from something and stole whatever it was, possibly small dead fish the wind had blown up against the island.  There was also a first winter Glaucous at this location that did not interact with the Glaucous-winged Gull.  After leaving the area I pulled into Cottonwood access and saw two large pale gulls flying around.  They were working their way west, towards the dam, and I could see that it was the same two birds I’d just left at Jack’s Creek.  The distance from Jack’s Creek to Cottonwood is about 1.5 miles (estimated).

How and when did you positively identify the bird, and what clinched the identification for you? I recognized this bird as a Glaucous-winged Gull almost immediately upon getting the binocs on it.  There just isn’t any other gull that has the overall concolor appearance, large black bill, and large size of this individual.  Continued study revealed the field marks mentioned above

How did you eliminate similar species, and what were they?

-Iceland Gull is much smaller and never show a bill as large as this individual.  In addition it has heavily checkered wing coverts, never solid bases to greater coverts.

-Glaucous Gull is eliminated by brown primaries and black bill.

-Herring Gull has blackish brown primaries, a much smaller bill with more squared off tip, usually pale based bill by this time of winter, typically more heavily checkered coverts, blackish tail, lacks extensive pale edges on primaries, and has longer primary projection.

-Western Gull also has blackish primaries and tail and longer primary projection.

-Slaty-backed Gull has darker brown primaries, longer primary projection, and much smaller bill. 

Hybrids between Glaucous-winged and both Western and Herring Gulls pose the biggest ID challenge.  Both are eliminated by primaries and tail concolor with rest of upperparts.  Glaucous Winged x Herring is further ruled out by the massive bill.  Since all field marks are well within normal range of Glaucous-winged, indeed almost everything is typical for the species, there is nothing to suggest the possibility of hybrid origin for this individual.

Experience with this species: I’ve seen one to several Glaucous-winged Gulls annually for about the past seven years, plus numerous individuals on a trip to CA. 

General experience birding:  14 years

Were photo(s), video, and/or audio obtained by you? No