[Birdtalk] California Gull vs Ring Billed Gull

[Cliff and Lisa Weisse]

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



Lofthouse wrote:
> "Is there any reliable way to distinguish
> California Gulls from Ring Billed Gulls
> at a distance?"
>  
> In my opinion, no.  When you have 2000+ gulls out on the water of the 
> Hyrum Dam at a distance of 1/4 to 1/2 mile I say, no way.  I don't 
> care how much you paid for your scope.
>  
> I had some fun at Walmart with a bag of popcorn.  Here is some 
> pictures.  There are birds of both species in the photos.  Have fun.
>  
> http://donce.lofthouse.com/jamaica/gull.htm
>  
> My observations:  The ring-billed is a bit smaller, and has yellow 
> legs where the California has greenish legs.  I cannot see any 
> difference in the shape of the bill as some have reported.  
>  
> The mantle of the ring-billed is a lighter shade of gray.  Be careful 
> using this mark though as the lighting can play tricks on you.
>  
> I can see no significant difference in the white spots on the 
> primaries, nor in the amount of black. 
>  
> The California does have a dark iris, and red on the lower mandible, 
> and red on the gape, and sometimes a little red is visible around the 
> eye.  None of these marks can be seen at a distance.  The ring-billed 
> has a light iris.
>  
> Some field guides show some brown streaking on the nape of the 
> California gull, but most of the birds in these pictures have a very 
> white head and nape.
>  
> Many times I enter "gull sp?".
>  
> What do you think?
>  
> Jim
>
>     ----- Original Message -----
>     *From:* birdnet at skylace.net <mailto:birdnet at skylace.net>
>     *To:* birdtalk at utahbirds.org <mailto:birdtalk at utahbirds.org>
>     *Sent:* Saturday, April 05, 2008 11:21 AM
>     *Subject:* [Birdtalk] California Gull vs Ring Billed Gull
>
>
>     Is there any reliable way to distinguish
>     California Gulls from Ring Billed Gulls
>     at a distance?
>
>     The reason I ask, is that during the winter
>     I sat on the flyway where gulls were coming
>     in to spend the night on a lake. About 200
>     gulls came close enough for me to see the
>     eyes. Every gull who's eyes I could see
>     had yellow eyes (ring-billed). 
>
>     The next day one of my favorite posters to
>     this group said that s/he had observed a flock
>     of California gulls at the lake.
>
>     So I went back to the lake and observed another
>     hundred gulls at close distance, and every
>     one of them had yellow eyes (ring-billed).
>
>     I think the other poster was wrong about the
>     identification even though s/he is very
>     knowledgeable about the birds of Utah.
>
>     Beyond about 100 feet I am clueless about whether
>     a gull is a California Gull or a Ring-Billed Gull,
>     and if even an expert goofs I wonder if eBird might
>     benefit from a California/Ring-Billed category?
>
>
>     _______________________________________________
>     Birdtalk mailing list
>     Birdtalk at utahbirds.org <mailto:Birdtalk at utahbirds.org>
>     http://utahbirds.org/mailman/listinfo/birdtalk
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Birdtalk mailing list
> Birdtalk at utahbirds.org
> http://utahbirds.org/mailman/listinfo/birdtalk

-- 
Cliff and Lisa Weisse
Island Park, Idaho
cliffandlisa at octobersetters.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://secureserver.securesites.net/pipermail/birdtalk/attachments/20080407/fc77bed7/attachment.htm