On November 9th, Tommy DeBardeleben found a young gull at the Glendale Recharge Ponds west of Phoenix that he initially took to be an odd Herring Gull. Sensing that something was odd, he sent photos around to others for opinion, and a quick consensus developed that the bird was in fact, a young Glaucous-winged Gull. This species is exceptionally rare in Arizona, with only six previous records for the state. Prior to Tommy’s sighting, the last Glaucous-winged Gull to appear in Arizona was eight years earlier, when one showed up in Palo Verde (see last image below). And prior to that, the most recent was back in 1981!
On November 13th, I headed to Glendale to look for the bird with fellow Tucson birder Deb Finch. Arriving at the recharge ponds, we quickly found others viewing the bird. The large, heavy-billed, chunky gull was in juvenile plumage, with essentially no replaced, second-generation feathers evident. Glaucous-winged Gull is closely related to Western Gull, and Glaucous-winged X Western and Glaucous-winged X American Herring hybrids are a common sight in wintering areas on the west coast. Because of this, extralimital birds are always scrutinized for hybrid characteristics. Determining what constitutes pureness in Glaucous-winged Gull is a bit like chasing rainbows. Most measures are subjective and in a birding context, heavily influenced by lighting conditions. Hybridization rates are really high in some areas in California and the Pacific northwest, and there may be no such thing as a completely pure individual. So subjective determinations are made as to what constitutes a hybrid for birders. Certainly there are clear cut examples, with birds that are pretty much intermediate between classic forms of the two species (where primary tips, secondaries, and tail are clearly and distinctly darker than the rest of the upperparts). But what of birds that appear just slightly darker, or have slightly more coarsely-patterned upperparts? Tough to say. The Glendale bird is darkish, but so are many young gulls in October and November. Flight shots do not reveal any really troubling features (i.e. darker primaries, secondary bar, or darker tail), and seem consistent with a juvenile Glaucous-winged Gull. If this gull were to be seen along the California coast at this season, it would be identified as a Glaucous-winged Gull by most without much hesitation.