[EBB Sightings] Mystery aythya-type duck at Lake Merritt, Oakland (Alameda Co)

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After looking at the photos, I believe it is a female Ring-necked  
Duck.  The other possibility is that this is a female Redhead Duck.   
The two ducks have been known to hybridize.   Glen is correct at  
eliminating it as a Pochard based on the slope of the bill and the  
forehead.  The Ring-necked  is a smaller duck than the Redhead but  
there is no duck in the photo to make a size comparison.   
Characteristics I look for to distinguish the two include the shape  
of the head, the female Ring-necked has a more pointed head compared  
to the Redhead's more rounded head.  The color contrast between the  
wing and the flanks is slightly more pronounced in a Ring-billed and  
includes a hint of a spur in front of the wings (very pronounced in a  
male).  The blue bill ring is narrower and more sharpely defined in a  
ring-billed than in a Redhead but there can certainly be overlap with  
this characteristic.  Also, there is slightly more contrast on the  
white patches surrounding the base of the bill on the Ring-billed as  
compared to the Redhead--but again there is overlap. I recommend  
checking out other photos of these two birds other than the pictures  
found in Sibley.  Kaufmans's guide has two good photos as a starting  
point.

Good birding as always,
Ted



On Nov 27, 2007, at 12:24 AM, Glen Tepke wrote:

> Wow, that is a strange looking bird.  Here is another photo of  
> female Common Pochard (Eurasian species, rare in Alaska, super-rare  
> in California) with somewhat similar plumage (most are duller gray- 
> brown than this):
> http://mangoverde.com/birdsound/picpages/pic27-120-1.html
> However, note that the Pochard has a sloped forehead and bill,  
> almost like a Canvasback, but your bird looks like it has a very  
> steep forehead.  Also, female Common Pochard in winter does have a  
> light ring around the bill, but it is not supposed to be so narrow  
> and sharply defined as your bird's.
> As you know, Lake Merritt is home to all sorts of released exotics  
> and domestic variants, so caution is in order, though if the bird  
> is associating with migratory scaup and has returned on its own for  
> the second year, that provides some circumstantial evidence for  
> wild origin.
> So, in conclusion . . . beats me, but thanks for posting.  Looking  
> forward to seeing what others think.
> Glen Tepke
> Oakland
> Hilary Powers wrote:
>> Stephanie Floyd wrote:
>>> Hilary Powers and I birded Lake Merritt in Oakland
>>> (Alameda County) this afternoon in search of the
>>> tufted duck and the hooded merganser x common
>>> goldeneye.  Didn't find those, but did find an unusual
>>> red-headed aythya-type duck on the lake just behind
>>> the Nature Center. It might be a female redhead, but
>>> the back looks more gray than brown....
>> This is quite possibly the same bird that I saw last year, and the
>> female redhead in Sibley was the closest thing as far as I could  
>> tell,
>> though others held out for a female ring-necked duck. I'm new  
>> enough to
>> birding never to have heard of a pochard, common or otherwise, the
>> red-crested pochard on Sibley's "Exotic Waterfowl" page having  
>> made no
>> impression at all. But one of the pictures Stephanie found online  
>> looks
>> so much like the bird at the lake, it's tempting to think it might  
>> be a
>> match:
>> http://upload.wikimedia.org/wikipedia/commons/thumb/9/9d/ 
>> Aythya_ferina_02.jpg/798px-Aythya_ferina_02.jpg Any ideas?
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Ted Robertson
Lawrence Hall of Science
510-642-4087




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