[Birdtalk] California Gull vs Ring Billed Gull

[Lofthouse]

"In your photos the long, narrow, parallel edged bill with blunt tip is particularly distinct on individuals in photos (counting down from the top) number 6 (both CAGUs), 7 (subadult furthest from camera), and 10."

The bills on all these gulls, of both species, have a very nicely rounded tip and a nice bump on the bottom mandible.  Parrallel  edged?    Blunt?  
Not what I would call it in either case.   

http://donce.lofthouse.com/jamaica/gullbill_0.jpg

http://donce.lofthouse.com/jamaica/gullbill_2.jpg

I appreciate your observations, and the things you have pointed out will be helpful to all of us.  

Jim 
  ----- Original Message ----- 
  From: Cliff and Lisa Weisse 
  To: Birdtalk 
  Sent: Monday, April 07, 2008 6:47 PM
  Subject: Re: [Birdtalk] California Gull vs Ring Billed Gull


  Jim,

  I have to disagree but first I'll say that variation in gulls is tremendous, illustrated nicely by your photos, and we're talking about subtle differences.  When I got interested in gull ID I was frustrated by my inability to see some of the differences I read about.  It takes practice and you have to look at a lot of individuals before you get a feel for it.  That said, in direct comparison I think you can tell the difference at 1/4 mile.  If you can see the mantle is it definitely a lot darker on California Gull.  Notice how much the white tertial crescent contrasts with the gray upperparts.  On CAGU you see obvious contrast but on RBGU it's not nearly as obvious and almost seems to blend into the gray.

  In your photos the long, narrow, parallel edged bill with blunt tip is particularly distinct on individuals in photos (counting down from the top) number 6 (both CAGUs), 7 (subadult furthest from camera), and 10.

  CAGU averages more black and more white on the primaries, with especially large white mirror on the outermost primary (P10) that sometimes extends all the way to the tip of the feather.  The adult in photo 12 has the entire tip of P10 white which I've never seen on a RBGU.  Also the flight feather are lighter gray than the mantle on Ring-billed.  In the right light you can see the bright whitish flash at distances that would surprise you but sometimes it can be difficult or impossible to see, like in the plate in my copy of Sibley.  

  In flight the wings of CAGU are longer and proportionately narrower than RBGU and the body looks longer/more slender.  This seems like a stretch but it can be surprisingly easy to separate these species in flight.  

  The legs on CAGU are duller in winter and bright yellow during breeding season.  In subadults they can be pink, grayish, greenish or even blueish.  The variation in leg color in your photos is dramatic.  Also CAGU often completely loses the black color on the bill during breeding season.  

  Something I forgot before - California Gull usually has extensive streaking on the head and neck that gives them almost a hooded appearance in flight that's very different from Ring-billed and is visible as far away as you can make out color.

  Hope all this is helpful but I offer a word of caution here.  Be careful how much you look at gull or you might end up standing in the mud in the freezing cold at a garbage dump wondering what happened to your sanity.  

  Cliff

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