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Summering Scaup Flock at Albany Bulb


Alexander Henry
 

Hi East Bay birders!

I just wanted to discuss the summering scaup flock at Albany Bulb. It seems historically that this area has hosted wintering Greater Scaups, and as Ethan Monk points out, Lesser Scaup are very rare in summer nearby portions of Contra Costa.

However, this summer, all conclusively identifiable photos of scaup taken at Albany Bulb have been Lesser Scaup.

Not to single out Dean LaTray, but I will use his photos as an example, simply because he has gotten the best quality, most clearly identifiable photos of these birds.

https://macaulaylibrary.org/asset/244400421

Here is one of Dean's photos. This is a straightforward male Lesser Scaup - which proves that there are summering Lesser Scaup in the area.

https://macaulaylibrary.org/asset/244606681

Here is another excellent photo - labelled as Greater Scaup - only, this bird is also, actually, a Lesser Scaup. I understand the confusion here, as the bird's head looks broad and rounded, however this is largely an artifact of posture. The spread wing pattern is distinctive - the white bar ends abruptly at the inner primaries, and the grayish outer primaries contrast the blackish primary coverts. This is diagnostic for Lesser Scaup. In a Greater Scaup, the white bar extends well into the primaries, but the outer webs of the outer primaries are black, not gray, so the outer primaries do not contrast as much with the primary coverts.
Also, the second male in the background in this photo is also a Lesser Scaup.

Anyway, my points are that 1) there are at least a few wintering Lesser Scaup at Albany Bulb and 2) there seems to be a tendency to misID Lessers as Greaters.

Have there been any Greater Scaups at Albany Bulb this summer? Perhaps a few have passed through, as there has been some turnover of individuals in the flock, but I stand by my assertion that the scaup flock at Albany Bulb this summer has been majority Lesser. It would help clarify the status if anyone could get a conclusively identifiable photo of a Greater Scaup at the Bulb in the next couple weeks though.


Ethan Monk
 

Hi Alex,

Thanks for the email! Since this seems at least partially directed at my backhanded eBird checklist comments, I figured I should respond in part (please don't take my checklist comments too seriously in there. Anything I find really important I'll put in an email here. All my comments meant is that people have the tendency to see 1-2 Lesser Scaup in a flock of Greaters, and extrapolate more Lessers into the picture). That being said, I would agree with you that there are several Lesser Scaup in the (a?) Scaup flock at the Albany Bulb/Pt. Isabel--I'll assume it's one flock sharing both locations. I think I've seen conclusive pictures of 2-3 Lessers. From my perspective, the majority of the flock has been Greater but I wouldn't feel confident in saying *all* of them have been Greater. While I do scope through them looking for the odd Lesser, as significant numbers of Lesser do winter here, I make the assumption that summering Scaup in the bay's northerly end are Greater (and vice versa with Scaup on the South Bay's salt ponds, which I know less about) and so I spend less time picking through them as I would in winter.This is probably something I shouldn't be doing.

We know that, historically, Scaup summering on this section of bayside have been almost exclusively Greater. I think you could say that Greater Scaup are the expected summering species in deep saltwater in much of Northern California? Whether or not the Lesser Scaup now are this year's exception or something previously overlooked, I don't know. If you'll notice, summer Lesser Scaup reports from the Albany-El Cerrito area in eBird are mostly exclusive to this year, but whether or not they've been overlooked in previous years we might never know.

To deal with the flock that's there right now--assuming they've been the same birds all summer, there are at least 18 Scaup around. We know from photos a couple are Lesser, sure. Telling how many are Greater from photos is harder, as generally people have a reluctance to photograph common and expected ducks, especially when they are in rather dull and tattered alternate. So I wouldn't make a blanket statement that since all of the 3 or 4 conclusive photos we've seen have been Lesser that the majority of the flock is Lesser. I'm willing to accept the possibility that the majority of the flock could be Lesser (as unlikely as that would be) but I think this is something that needs more study before we can say anything conclusive. I don't think just one photo of one Greater Scaup will cut it here.

Luckily for us, the flock should stick around for a while longer, and we all have a chance to figure out what's going on here. Greater Scaup are a rapidly declining species, so perhaps Lessers are moving in to fill in for the lack of Greaters? Anyway, I'll change my eBird lists so that half of the flock is a slash. I'll update them further as we find out more.

Thanks!
Ethan Monk


Alexander Henry
 

Thanks for the reply Ethan!

I should not have said the majority of the flock is Lessers - clearly there are a good number of Greater Scaup around. But there is also a fair number of Lesser Scaup around. I think you are probably right that I saw several obvious Lessers in a group and made assumptions I should not have about the rest of the group.

Before this discussion, I genuinely didn't realize that Lessers were unusual in the area in summer; I should've been more careful and looked up the historical status. However now that we know there are several Lessers summering in the area, I think a reexamination of summer scaup status is in order.

I also went back and changed most of my sightings of this flock to Greater/Lesser. I think I will probably be using this option more often in the future, especially with ratty summer birds, or otherwise will pay closer attention to each individual in the flock.

Also, its possible that, among the larger flock of scaups moving around in the general area, there is at least some degree of associative flocking or subflocking. Usually there is at least some of this in winter, with the Lessers preferring to hang out with other Lessers, and the Greaters preferring the company of other Greaters. (Of course they often mix together as well though).