A Brit abroad

Harlequin Scoter

I just returned from a fantastic weekend at the Central Valley Birding Symposium. I'll post more about that later, but first I'd like to throw my two cents' worth into the debate about an unusual duck found on one of the symposium field trips to Stockton Sewage Ponds. First identified as a Harlequin Duck (only the second county record and possibly only the fifth for the Central Valley), several observers subsequently decided it more resembled a female White-winged Scoter, primarily on the basis of its large-looking bill. I still consider this bird to be a Harlequin: I'll present the case for the defense after these photos.

1. "Jizz". My evaluation of the bird's size was that it was a small duck, not an impression I would expect from a White-winged Scoter, being the largest of the scoters.

2. Behaviour. The bird was feeding continually on a drainage ditch, right at the edge of the rocks, submerging only its head rather than diving. It even climbed out onto a rock at one point (photo 3), behaviour consistent with Harlequins I have seen along the coast. I would have expected a scoter to be out in the middle of the sewer ponds and diving for food. Of course, either bird was far from home in Stockton, so we might expect unusual behaviour in a novel environment.

3. Bill. The main feature supporting the identification as a White-winged Scoter is the apparently large bill shown by this bird. The bird spent most of the time we watched it with its head underwater (the reams of 'headless' photos of this bird on my camera are testament to this), which can flatten the crown and dramatically change a bird's head shape, making the bill appear proportionately larger than our perception of a round-headed, small-billed Harlequin. Personally, having looked at many photos of White-winged Scoters recently, I believe this species shows a much longer bill than the bird pictured here.

4. Eye colour. The bird we saw unequivocally showed red eyes (photos 1 and 2). While I see no explicit reference to eye colour as an identification feature in Sibley, in an exhaustive Google image search, I have not yet found a picture of a scoter showing a red eye (which Harlequins do).

5. Face pattern. The bird showed a clean white circular spot on the cheek. The pale areas around the face were less clean, but the bird clearly showed pale patches above the line between the eye and the bill (the extent to which this feature was visible varied with angle).

I rest my case (but comments very welcome!)

As a postscript to this entry, most people have finally come to a consensus that this bird is indeed a Harlequin. Further pictures and more detailed discussion of the bird can be seen on Don Roberson's website and in the 'Ducks' folder of Chris Conard's website.

Posted by rjhall at November 21, 2005 4:56 PM