Age: At first glance this appears to be an adult, or an adult-type, large white-headed gull. The light gray tips to the median coverts are reason enough to suspect this is a sub-adult bird.
Identification: This month's quiz bird is dark-backed with rich yellow legs. There aren't many species that meet this criteria in North America. Lesser Black-backed Gull, California Gull and Yellow-footed Gull should all be considered.
I will dismiss California Gull on the count of it being a noticeably paler species than what is seen here. On the palest end, California Gull scores a 5 on the Kodak Gray Scale, and a 7.5 on the darkest end. The palest Lesser Black-backed Gull (subspecies graellsii) scores a 9 on the Kodak Gray Scale, and a 13 on the darkest end (nominate fuscus - unrecorded in North America). Yellow-footed Gull (monotypic) ranges 9-10.5.
We are left with Lesser Black-backed and Yellow-footed Gull. The bill on our bird is thick all throughout and shows a noticeable bulbous tip. This seems much better for the Mexican species. Zooming in we note a darkish iris and yellow orbital. Adult type, and even many sub-adult Lessers, show eyes that are considerably paler than this. Lesser Black-backed also sports a reddish orbital ring.
Our quiz bird is indeed a Yellow-footed Gull photographed at the Salton Sea in Imperial County, California. September.
I will dismiss California Gull on the count of it being a noticeably paler species than what is seen here. On the palest end, California Gull scores a 5 on the Kodak Gray Scale, and a 7.5 on the darkest end. The palest Lesser Black-backed Gull (subspecies graellsii) scores a 9 on the Kodak Gray Scale, and a 13 on the darkest end (nominate fuscus - unrecorded in North America). Yellow-footed Gull (monotypic) ranges 9-10.5.
We are left with Lesser Black-backed and Yellow-footed Gull. The bill on our bird is thick all throughout and shows a noticeable bulbous tip. This seems much better for the Mexican species. Zooming in we note a darkish iris and yellow orbital. Adult type, and even many sub-adult Lessers, show eyes that are considerably paler than this. Lesser Black-backed also sports a reddish orbital ring.
Our quiz bird is indeed a Yellow-footed Gull photographed at the Salton Sea in Imperial County, California. September.