WESTERN GULL in Idaho

by Harry Krueger
(Adapted from message to IBLE, 25 December 2004)



Photo © 2004 Cliff & Lisa Weisse

When it comes to identifiable subspecies, you all probably know I have difficulty resisting. So, between careful multiple and close personal observations, great pictures (Cliff Wiesse), and a new gull book for Christmas (Gulls of North America, Europe, and Asia) I've come to the following conclusion regarding the 1st winter Western Gull that continues to be seen at the Canyon County Landfill (Pickles Butte) (photo above):

After Cliff and Lisa Weisse originally found the bird and felt that they might have a legitimate Western Gull, when I saw it again in their company the following day, my comment was that from what I was seeing, the bird seemed to represent a perfect 1st winter Western Gull. Upon closer and repeated observations, that conviction was reinforced. Interestingly, when pictures were sent to a Northwest coastal "gull expert," his comments were that everything looked great, and even though it was a bit darker than he was used to, he chalked that up to the fact that maybe this was even a "purer Western" than he was used to seeing. Let's back up a moment.

There are two subspecies of Western Gull along the West Coast, Larus occidentalis occidentalis, which is the nominate race, and L. o. wymani. The former breeds coastally from central Washington to the Monterey Peninsula, CA and the latter generally from San Francisco and south. The more northern bird (L. o. occidentalis) is non-migratory and fairly sedentary after the breeding season, whereas wymani is migratory and moves north coastally all the way to s. British Columbia in winter. Both birds hybridize with Glaucous-winged Gull, but probably much more so in the case of occidentalis. Purely from seasonal movement perspective, an inland Northwest observation is much more likely to be the southern race, wymani, although very young occidentalis do migrate north in a post-fledgling dispersal movement. Obviously, winter dispersal is not proof in itself or reason to assign the Canyon County bird to any particular subspecies, although this is corroborating evidence.

In observations initially made (and comments received) it was noted that the bill shape was correct for Western Gull but did not match the usual description of a thick and bulbous tip; it just seemed a bit "slimmer." L. o. wymani has a slightly "less heavy bill" than L. o. occidentalis. Also, wymani does not seem as short, stubby and heavy bodied as occidentalis...consistant with impressions of this bird.

The overall color was judged by some to be somewhat darker and more contrasting than expected (although it was consistant for me with what I was used to from Southern and Central California), especially the head "mask" or half-hood, breast, with "washed out" throat area to sides of neck and definitely the paler hindneck. This is all perfectly consistant with wymani but not occidentalis.


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