Iceland Gull (Larus glaucoides)
Fort Baker, Marin County CA
7 February 2012
Joseph Morlan
Photo © 7 February 2012 by Joseph Morlan. All rights reserved (High resolution).
After hearing reports that Todd Easterla had found two Slaty-backed Gulls at Fort
Baker in the Marin Headlands, Robbie Fischer and I decided to try for these birds as well as the continuing Iceland
Gull. Upon arriving around 4:00pm, we learned that the adult Slaty-backed had flown off sometime earlier. I was
particularly interested in seeing the Iceland Gull having missed the bird on 4 February by leaving too early before
the bird came in.
I could see no evidence of the Iceland Gull in its usual haunts in a cove north of the Coast Guard pier and
most of the attention was focused on an immature gull which was being called a second
cycle Slaty-backed. After photographing the presumed Slaty-backed, Robbie and I headed back to the cove hoping
that the first cycle Iceland Gull might have returned. Eventually Dan Singer joined us and he rather quickly spotted
the bird at the far end of the beach. I took a few photos and was heading up to get closer to the bird when Josiah
arrived on his bicycle and all the gulls flushed. The bird eventually returned to the beach just north of the fishing
pier where we could view it at close range, but it was almost 6:00pm by then and too dark for photos.
Description
The following description is based on memory and on photos:
A medium sized gull, about the size of nearby Thayer's Gull but with a more petite bill with a pale base.
The body was mostly white with pale brown shading, slightly darker on the body and with finely mottled wing
coverts and tertials. The wing tips were almost entirely white with no obvious markings. The tail coverts were
strongly barred with light brown which extended across the base of the tail. The distal two thirds of the tail
was light brown with a paler tip.
The eye was dark; the legs were short and pink.
Discussion
This bird was originally found by Steve Hampton 2 February and has been seen most days since, usually in the
cove at the northwest corner of the harbor. When evaluating candidate Iceland Gulls from the Iceland/Thayer's spectrum
I usually go back to the characters itemized in the 1997 Annual Report by Rottenborn and Morlan, "It is thought
that "pure" Iceland Gulls in juvenal plumage generally show (1) whitish tertials lacking extensive interior
markings, (2) pale outer primaries concolor with or paler than the tertials and inner primaries and showing extensive
white fringing, (3) pale secondaries without dark markings and not showing a dark secondary bar, (4) a pale tail
without an extensive darker tail band, and (5) pale mantle feathers with limited dark internal markings (cf. Zimmer
1991)." In addition, good Iceland Gulls have the eye diameter at least a quarter the length of the culmen.
I believe this bird scores well in all five characters. Several competing scoring schemes have recently been
proposed, one by Floyd Hayes and another by Steve Hampton. This individual seems to score well on the Iceland side
in all features.
The subspecies of this Iceland Gull has been the subject of some speculation but there is so much variation
in both kumlieni and glaucoides, that I prefer to leave the question open. This area is on the boarder
between Marin and San Francisco Counties. Analysis by Mark Eaton here.
External Links
Other photos have been posted as follows: