Possible Slaty-backed Gull, Larimer

[Nicholas Komar]

A first cycle large white-headed Gull at Horseshoe Reservoir in Loveland (Larimer) seems to check most boxes for Slaty-backed Gull. See photos below. Warning: this age/species combo is very difficult to confirm so may not get confirmed in eBird or accepted by a records committee. But wanted to share to give folks an opportunity to look for it.

[ColimaBirder]

Most lariphiles agree some first cycle pale-headed gulls are challenging.  So much variation. 

Can you you elaborate on those “checked boxes” you mention?  

Bruce Webb

Former Boulder resident 

On Sun, Mar 28, 2021 at 11:42 AM Nicholas Komar <quet...@comcast.net> wrote:

A first cycle large white-headed Gull at Horseshoe Reservoir in Loveland (Larimer) seems to check most boxes for Slaty-backed Gull. See photos below. Warning: this age/species combo is very difficult to confirm so may not get confirmed in eBird or accepted by a records committee. But wanted to share to give folks an opportunity to look for it.

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Nick Komar
Fort Collins CO

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Bruce Webb
Granite Bay, California

[Dave Cameron]

Has anyone had occasion to go search for this bird since the 28th?  Any info as to whether it's still around would be appreciated.  Thanks!

Dave Cameron

Denver

[Nicholas Komar]

Sorry I meant to follow up. I read up on first-cycle Slaty-backed Gull Identification. While this bird looked similar, a couple features in particular ruled out Slaty-backed Gull. The outer wing (a.k.a. the hand) was long like Herring and Glaucous-winged, rather than short. Also the bill was very long with the curvature of the culmen well anterior to the nostrils. In Slaty-backed, the bill is short with the curvature beginning over the nostrils. Therefore I concluded that this bird was not Slaty-backed but rather a hybrid Gw x herring. This hybrid combo is becoming more frequent among our winter gulls, and is well known to appear similar to slaty-backed gull in first cycle plumages. 

I have been keeping an eye on the Larimer gull flock and have not seen this bird again. 

Nick Komar

On Apr 6, 2021, at 4:48 PM, Dave Cameron <dave...@msn.com> wrote:

Has anyone had occasion to go search for this bird since the 28th?  Any info as to whether it's still around would be appreciated.  Thanks!

To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/0894704b-5de1-46b6-b8ba-8ff7d8e52132n%40googlegroups.com.

[Dave Cameron]

Thanks, Nick, for the explanation.  And, it saves me a trip!  

- Dave Cameron