ML118424501

Age and sex

Adult, Unknown sex - X

Observation details

As I started to scan the gulls on the wharf roof, I immediately noticed a GWGU-sized glull with a blackish-gray mantle. Viewing conditions were very good and I was using a new 85 mm Swaro scope. I could see more detail by scope than I could capture by camera. (My 400 mm lens gets strained at that distance.) The gull remained on the west edge of the roof, as far away as it could be and still be on the roof. I watched the gull for about an hour and a half before it flew off with other gulls leaving the roof. I made a number of calls but was unable to reach any local birders who were free to come to this site. I finally got in touch with Josh Adams who had a long drive. Unfortunately, Josh arrived shortly after 6 p.m., at the very moment that the target gull left the roof with other gulls. We looked for two more afternoons but the gull did not return and gull numbers on the roof were about one third the number present on this day. Field marks I saw: 1. slate gray mantle on an adult gull 2. brightish pink legs (brighter than what I could capture in photos) 3. lightly, but noticeably streaked head (not picked up by photos) 4. light iris (not picked up by photos) 5. dark slashes through the eyes 6. yellow bill with red dot at the end of the lower mandile 7. some black at the tips of the primaries with white dots 8. large tertial crescent I did not clearly see the string of pearls field mark because I was distracted by Josh's arrival at the moment the gulls flew. I recently returned from a trip to western Alaska where I saw a fair number of SBGUs. Between size and leg color, I could rule out LBBG. I considered a WEGU of the southern population with its much darker mantle, but an adult WEGU does not have the distinctive dark slashes through the eyes that are seen on a SBGU. A GBBG would have a mantle as dark as that of this gull and it would have pink legs, but when compared to the other large white-headed gulls on the roof, this gull was the same size, not larger. And an adult GBBG would not have dark slashes through the eyes.This bird reminded me of the Port of Tacoma gull. Viewing conditions are described in the checklist general comments.

Technical information

Model

NIKON D7200

ISO

1250

Focal length

400 mm

Flash

Flash did not fire, auto

f-stop

f/5.6

Shutter speed

1/500 sec

Dimensions

1462 pixels x 1049 pixels

Original file size

553.6 KB