My first stop was along the Duwamish River in Tukwila. Decent numbers of Thayer's Gulls (200+) are found on the rooftop of the Yellow Freight Truck Company:
|Another ineffective owl decoy among a flock of Thayer's and Glaucous-winged Gulls.|
|First cycle Glaucous-winged (left) and Thayer's Gull (right). Tukwila, WA. 30 Dec 2011.|
Adult Thayer's Gull. Duwamish River in Tukwila. 30 Dec 2011.
And another one in flight:
Although Glaucous-winged Gulls are year-round residents in Western Washington, it wasn't always obvious which birds were "pure". Here are several well within the limits of GWGU:
|3rd cycle. Mouth of the Cedar River. 01 Jan 2012.|
|Adult. Sayer's Park. 03 Jan 2011.|
|2nd cycle. Tukwila, WA. 30 Dec 2011|
Adult Western Gull. Ocean Shores Marina. 02 Jan 2012.
Many others fit the Western profile but showed some combination of cloudy head markings, barring on the neck, pale eyes, paler bill and/or paler upperparts like this bird:
Hybrid tending towards Western Gull. Sayer's Park 03 Jan 2012
The copious number of hybrids at every site I visited made for some very interesting identifications. It's worth noting that the hybrids in the Puget Sound area have a much more Glaucous-winged look to them, whereas birds on the coast tend to display more Westernish traits.
Consider this 1st cycle bird:
On the surface, its plumage matches Thayer's, but size and structure are sufficient for ruling out that species. The larger bill, muscle-neck, sagging belly and broad wings all point to a larger taxon - this is a typical Olympic Gull. Side-by-side comparisons are much easier than assessing lone birds:
|Thayer's Gull (left) with Olympic Gull (right). Note how hybrids tend to show a secondary skirt. This is due to the broader wings (longer secondaries) inherited by both parent species. Sayer's Park. 03 Jan 2011.|
Here's another Thayer's look-alike but note the overly large proportions for that species:
A few more Olympics:
What follows is a set of non-1st cycle hybrids that represent both ends of the continuum. Try to assign various traits to each parent species:
|2nd cycle. Duwamish River in Tukwila. 30 Dec 2011.|
|2nd cycle. Ocean Shores, WA. 02 Jan 2012.|
|2nd cycle. Gray's Harbor, WA. 02 Jan 2012.|
3rd cycle. Ocean Shores, WA. 02 Jan 2012.
Adult. Ocean Shores, WA. 02 Jan 2012.
There seemed to be no shortage of Glaucous-winged x Herrings (so called Cook Inlet Gulls). These individuals tend to show smaller bills that are bicolored and paler scapulars than Olympics. Compare the next two birds:
|Pure 2nd cycle Glaucous-winged. Mouth of the Cedar River. 01 Jan 2012.|
|Presumed 2nd cycle Glaucous-winged x Herring. Duwamish River 30 Dec 2011. |
Here are a few more 2nd cycle Glaucous-winged x Herrings:
|Presumed 2nd cycle Glaucous-winged x Herring. Mouth of the Cedar River. 01 Jan 2012.|
|Presumed 2nd cycle Glaucous-winged x Herring. Sayer's Park. 01 Jan 2012.|
This is the only adult that I felt confident enough to call a Glaucous-winged x Herring:
Presumed Cook Inlet Gull. Tukwila, WA. 30 Dec 2011.
Another objective of mine for this trip was to gain more field experience with subadult Mew Gulls (L.c.brachyrhunchus). Although I've observed decent numbers of Mews in my visits to California, most were adults. I was very "fortunate" to visit the Metro Sewage Ponds on New Year's Eve with the Discovery Park CBC party. Many of the locals preferred to stay out of the sewage ponds on this day but I readily accepted the job of going in and counting, one by one, 658 Mews. I couldn't imagine a better way to spend the last day of the year!
|1st cycle Mew Gull. Metro Sewage Ponds. 31 Dec 2011.|
|2nd cycle Mew Gull. Metro Sewage Ponds. 31 Dec 2011.|
|Adult Mew Gull. Metro Sewage Ponds. 31 Dec 2011.|
From an identification standpoint, some 1st cycle (and perhaps even 2nd cycle) individuals can superficially resemble Ring-billed, but after seeing enough 1st cycles on this trip, I'm convinced that there really is no way to confuse the two in the field (given more than a snapshot view). Besides the more petite bill and dove-like head of Mew, its uppertail and undertail coverts differ
tremendously from RBGU:
One thing I noticed on all of the 1st cycle Mews on this day was that none had replaced any of the upperwing coverts or tertials. By late Fall, the overwhelming majority of Ring-billeds will have some new (gray) feathers on the upperwing like this bird:
|1st cycle RBGU. The gray greater coverts and gray tertial feather effectively eliminate first cycle Mew Gull.|
Chicago, IL. 05 Nov 2011.
Mew Gulls will, at best, show faded or bleached upperwing coverts before the 2nd prebasic molt and so this could help avoid confusion with similar aged Ring-billeds:
|1st cycle Mew Gull with the entire upperwing panel showing first basic feathers. Sayer's Park. 03 Jan 2012.|
Another common feature that I noticed on these first year Mews is pale edging on the primaries tips:
This individual below is the closest I could find to a Ring-billed-look-alike, structurally:
|1st cycle Mew. Sayer's Park. 03 Jan 2012.|
|Note the neatly barred uppertail coverts that are not shown by Ring-billed.|
Here's a nice comparison of a 2nd cycle MEGU and RBGU photographed during the same session:
|2nd cycle MEGU. Sayer's Park. 03 Jan 2012|
|2nd cycle RBGU. Beside the thicker bill and paler upperparts, Ring-billed averages a much smaller mirror on P10 and lacks the thick trailing edge shown by Mew. Seward Park. 03 Jan 2012.|
As for identifying adult MEGUs, Ring-billed would be easily eliminated.
I photographed these adult Mew Gulls just hours before concluding my trip and heading to the airport. All were photographed at Sayer's Park on Lake Washington:
I'd like to thank Seattle's go-to-guy for gulls, Michael Donahue. Michael was kind enough to spend an entire day showing me around and birding with me. I was moved by his knowledge of the area's gulls which was nothing short of impressive.
The Puget Sound area certainly possesses a unique dynamic of North American larids. Something tells me I'll only be able to stay away for so long before going back!