Monday, January 12, 2009

Another Greater Scaup! or NOT....

Blogger's note 1/13/09: See comments to this blog entry. I always listen to the opinions of David Ringer. His thoughts and insight into bird identification are thorough, and he always asks the right questions. After reading his comment on this post, I investigated. The comments that struck a chord with me were not about the "nail" (Sibley guide says there is much overlap), but the one about a feeding, threatened or alert Scaup.

From
http://www.biology.eku.edu/kos/scaup.htm , I quote: "Images E and F depict how head shape can change with attitude. Lesser Scaup typically compress their head feathers when feeding eliminating the peak to the crown which gives them a totally different appearance. They may also do this when alert or threatened. They can appear very similar to Greater Scaup when assuming this attitude, particularly when showing a green gloss to the head."

Perhaps the Scaup of this post is a Lesser, and the three Scaup of the previous post are Greaters. Or perhaps all are Lesser. I've learned a lot about Scaup through these sightings and follow-up blog entries.

Birders have come down on both sides of the fence on the original post called "The Scaup Scoop". Perhaps I should return to Robbins and Easterla's comment,
"the only reliable field mark for distinguishing these two species is the extent of white on the upper side of the primaries."

Original post:
Well, today I seemed to have run into another rare Greater Scaup in the Ozarks. This individual did not have the striking green head of last Thursday's birds, but the gizz sure seems right to me. Check out the wide head on the bottom pictures. What do you think?








4 comments:

david said...

Hi Greg,

One thing that bothers me about these pics (and the previous ones) is the narrow black nail on the bill. It's certainly not a nice triangular wedge. But apparently this feature is variable, like the rest?

The head is very flat in all these pics, which indicates that the bird was not relaxed and thus that the 'true' head shape is masked. Lessers can show very flat heads.

In your pics from the other day, none of the birds seem to show a nice strong peak high on the head -- i.e., over or even in front of the eye. Instead they seem peaked toward the rear.

But as I just said, head shape varies depending on what the birds are doing.

I am not familiar enough with the pair (particularly Greater) to make a firm statement either way. I don't feel that these are 'classic' Greater, but perhaps they are within an acceptable range of variation (i.e., overlap?).

David

Greg said...

Hi David,
I was awaiting your comments and found a website that addresses your concerns. Thanks for the input. http://www.biology.eku.edu/kos/scaup.htm

I'm at work now, but will search more later.

Jochen said...

Without having seen the birds myself, it is very difficult to come to a conclusion or say anything useful.
I have quite extensive field experience with Greater (a few 100,000 over many years in Germany) but have only seen Lesser during a relatively short period of time (a few 100 during 1 year). It is thus difficult to judge the "Gestalt", the general appearance, which is quite different most of the time between the species.
Nevertheless, your birds do look quite a lot like Greater, especially the ones in the first post. I would have identified them as Greater had I seen them, or - as I am now stationed in Germany again: would I see them here, where Lesser don't occur but Greater are regular, I wouldn't find these birds unusual.

However, I can easily see why a records committee would struggle to accept the observations if the species was a great rarity and the only absolutely reliable field character, the extend of white on the primaries, wasn't seen or isn't documented.
So I think you can quite confidently put the species on your life list, but if your record will be included in the scientific data base is another question...

Greg said...

Jochen,

Thanks for your comments! They certainly serve to boost my sagging self confidence. I have decided to call the first sighting birds Greaters even though I fully realize the important of the white extension on the outer primaries. I found a duck hunter site that said that in hand, the Green heads of a Greater are easily differentiated and identified, and the first birds did have strikingly green heads accompanying other field marks that favor Greaters. Second sighting: Probably a Lesser.