Adult “Olympic Gull” in San Diego

I took these photographs of an adult basic (winter) plumage “Olympic Gull” (Glaucous-winged Gull x Western Gull) back on December 13, 2011 while visiting Lindo Lake in Lakeside. I had just started walking around the perimeter path of the lakes when suddenly I noticed a large light grey colored gull flying in my direction! I only managed to get a flight shot as it was flying away.  It made a bee-line over to the floating wooden raft, in the duck-feeding area of the lake, so I ran around the west lake as quickly as possible to investigate.

One of the most noticeable features of this gull is the coloration of primary feathers which fade from the grey of the upper-wing to the black of the primary tip – very unusual. This individual shows other characters typical of this hybrid parentage including a heavy bill morphology, angular shaped head, darker flecking of the head feathers, an intermediate grey (between Glaucous-winged and Western Gull) colored mantle and upper-wing, and a bulky looking skirt of secondary and tertial feathers.

Whether this is a first-cross between the parental species, or some degree of back-cross of a hybrid with one parental species is unknown.  I suppose with the large frequency of hybrids reported in the zone of hybridization anything along the spectrum from Glaucous-winged to Western Gull could possibly be found.  This individual does match well to examples of adult basic (winter) plumage “Olympic Gull” that I could find on the internet. The eye-ring appears a rich yellow while the iris is greyish-yellow (brown?) with tiny darker flecking present – these characters seem more in line with Western Gull than Glaucous-winged Gull. The published literature however does make reference to intergrade individuals potentially having eye-ring and iris color matching either parental species.

Hybrid Glaucous-winged x Western Gull are uncommon in winter in San Diego County although some good gull spots attract a handful of birds which are invariably first-cycle individuals.  I guess there could be some reporting bias if second-cycle birds are more confusing to observers.  Reports of adults seem non-existent however, I checked through the SDBIRDS archive but could not find any previous records of adult “Olympic Gull” in San Diego County in the winter months.

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