[Birdtalk] California Gull vs Ring Billed Gull

[Cliff and Lisa Weisse]

I'll take a stab at this.  First, consider the possibility that both 
Ring-billed and California Gulls roost at that location.  That said 
there are definite differences between these species, even in flight at 
a distance. 

Adult California has a darker mantle, so it appears to contrast less 
with the black wing tips.  Mantle shade can look quite variable 
depending on angle of sun so be cautious when using this mark.  
Ring-billed also has lighter gray between the black wing tips and the 
gray of the mantle and inner wings.  This bright flash is visible at 
considerable range.

Adult California tends to have more extensive black on the wing tips but 
both species vary a lot.  California also tends to have larger white 
spots on the outer primaries. 

Shape can also be useful.  To me Californias are fairly easy to 
recognize by the longer, proportionately narrower wings and slender 
body.  Ring-billeds look stubbier bodied and shorter winged in flight.  
These structural traits can be seen from a long way off.  Shape has the 
advantage that it can be used for all ages. 

Another thing that really helps me is the bill on California Gull.  It's 
long and thin with square cut tip and almost no visible bulge at the 
gonys.   No other North American large gull has a bill shape like this.  
They're either shorter and thin or bulkier/thicker and often have 
pronounced bulge at the gonys.  With practice you can recognize that 
shape easily even if you can't see the color well. 

Hope this is helpful.

Cliff



birdnet at skylace.net wrote:
> 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?
>
>
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>
>
>   

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