[Tweeters] Gull ID Questions

Keith Carlson kec201814 at cableone.net
Fri Dec 23 16:30:58 PST 2016

A recent gull sighting has caused me to raise several questions for which I have no or few answers.
If gull ID's cause you to glaze over, now is probably the time to quit reading.
Yesterday, I observed and photographed this gull at the Asotin County Landfill for about twenty minutes.
One of the first challenges is to age the gull.
In this case, both the Ring-billed Gull and the Mew Gull have white tails with a black band until they are adult birds, at which time the tail becomes all white
Since this bird has an all white tail, one would judge it to be a non-breeding adult.
I'm assuming, perhaps incorrectly, that to achieve an all white tail requires a rather complete molt.
Gulls of the Americas , Howell and Dunn  states that perhaps 13% of 2nd cycle Mew Gulls and some RB Gulls  obtain an all white tail during molt.
But this bird has no or few other adult characteristics of either RB or Mew Gull.
An adult RB should have a yellow bill with a black ring, yellow legs and a clear eye.
An adult Mew Gull should have a yellowish bill with no or little black banding, yellow legs and a dark eye.
Most experts, but not all, I have consulted on this particular bird ID it as a RB Gull
My conclusion is that it is a 2nd cycle Ring-billed Gull that has undergone a minority molt resulting in an all white tail and has not yet obtained yellow legs.
My final conclusion is that reliance solely on field guides will often result in very confusing ID problems.
Keith Carlson

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