[birding] Mystery Goldeneyes

[David Irons]

I would concur with Alan Contreras on these birds, they are definitely Common and not Barrow's Goldeneyes.  The bird on the left appears to be a female, while the bird on the right appears (at least in these images) to have just a hint of the white facial spot starting to show between the eye and the bill, which would indicate that it is a young male. When separating female and immature male goldeneyes, the key things to look at are bill length, bill slope, slope angle change between the forehead and bill, crown profile, and forehead slope (the latter being the most plastic structural clue).

Barrow's Goldeneye -- The bill of a Barrow's usually looks rather small, short, and somewhat stubby compared to that of a Common Goldeneye. The forehead slope of a Barrow's is quite steep bordering on vertical. The slope of the bill often looks a little steeper on Barrow's, likely an illusion created by the fact that it is shorter. On Barrow's, the high point on the crown is usually in front of the eye and the crown is otherwise somewhat flat looking with a gradual slope towards the nape. Finally, there is usually a fairly obvious slope angle change between the line of the near vertical forehead and the 45 degree slope of the upper mandible.

Common Goldeneye -- The bill of a Common usually looks larger overall, longer, and rarely looks stubby compared to a Barrow's. Commons have a more angled forehead slope and often times the angle change between the forehead and the bill is almost non-existent. The highest point on the crown of a Common Goldeneye is usually more towards the middle, typically almost directly above the eye. This creates a peaked look to the crown (see illustrations in Sibley Guides). All this being said, it is important to recognize that the angle at which the head is being held can significantly alter the appearance of the crown profile and forehead slope. When Common Goldeneyes are swimming away from the observer and looking slightly to the side the forehead can look very steep and this angle makes the bill look shorter as well. I think the fact that Matthew's birds are swimming away and not in direct profile is part of what makes them a bit problematic. 

Bill Color -- While the presence/amount of yellow on the bill can be a helpful clue, it is not (as was once thought to be the case) a very reliable way to separate these species. Generally speaking, Barrow's show more yellow and lots of female Commons show now yellow whatsoever, but this is highly variable. 

Dave Irons
Eugene, OR 

> From: cncschneider at msn.com
> To: obol at oregonbirdwatch.org; list at midvalleybirding.org
> Date: Thu, 7 Jan 2010 19:19:23 -0800
> CC: 
> Subject: [birding] Mystery Goldeneyes
> 
> Hi Birders,
> 
> On Silverton's CBC(Saturday January 2nd.) there was a pair of Goldeneyes sp. 
> on a reservoir just SE of Silverton. The four pictures of the Goldeneyes can 
> be viewed at:
> 
> http://www.oregonbirds.org/birdphotos.html
> 
> The pictures aren't the greatest since the birds were approximately a 
> quarter of a mile from the photographer.  Both species of goldeneyes have 
> occurred on the CBC.  There also were two first winter male Common 
> Goldeneyes on another sector.  The two Common Goldeneyes had a distinctly 
> different face pattern then the pair in the photos.  Any ideas?
> 
> Thanks in advance.
> 
> Matthew Schneider
> Silverton, Oregon
> Assistant Compiler for the Silverton CBC 
> 
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