Date: 6/20/20 12:10 am From: Robert O'Brien <baro...> Subject: [obol] Re: White-rumped vs. Semipalmated Sandpiper?
Right, I'm aware of variation in bill length in many shorebirds with females usually having longer bills. Western Sandpiper is an excellent example, easily seen in any sizeable flock.
But I'm not talking just about bill length, although that is included, but also about bill shape. Relatively blunt vs. relatively sharp. I am invariably able to pick out fall Semi Sands (vs. Western) in Oregon immediately by their bill _shape_. Now that could mean I miss a lot of them. But I don't 'identify' them by their bill, I recognize them by their bill before looking at other plumage features. These are noted as well. If you look at Macaulay library for Aug-Sep Semi Sands in Oregon you will see what I mean. There is very little variation in them. Short and relatively blunt.
Which brings up one of my original questions. * Are the fall semi's bill still growing and will get longer and sharper? Is this possible?* We see very few adult(?) Semis in Oregon in spring, so not much data on that front. They are quite rare and would be expected to be rare in Washington as well, I guess
The sandpiper I originally brought up looks nothing like the Aug-Sep, Oregon, Macaulay Semi Sand photos in bill shape/length as I am familiar with in Oregon. And I believe its primary projection is within the range of White-rumped.
If you look through June White-rumped in Macaulay, you will find some that have breast streaking not all that different from the bird I referenced originally. Lars was referring to high breeding plumage and not all are in that plumage in June. They may be first year birds, or just not as far along. In fact I believe I've read that in their first year some (many?) shorebirds go north but do not go all the way to their breeding grounds and do not acquire full breeding plumage. This is not unusual at all. (This is from memory, I haven't looked it up now). And June 14 would be late for any shorebird intent on breeding. for example there was only a single other shorebird, a Greater Yellowlegs in the report. They are 'gone' by June 14 if they are indeed 'going' at all.
Now, if you look for Lars' other point, a pale coloration at the base of the bill, most but not all June White-rumped in Macaulay have this mark. In some cases very faint and just at the very base of the bill, while in others extending considerably further. I would guess it is associated with high breeding plumage.
Based upon the clear all-dark bill of the bird in question I would guess that it likely is indeed a Semi Sand as reported. But it would be helpful to see additional photos -- of the breast full on and especially of the rump upon takeoff. I'm not claiming to identify the bird in question by the bill. My original comment said *suggesting * That is, I would have been happy to see additional photos for verification.
Bob OBrien Carver OR PS: Shorebirds are the Best Birds
On Fri, Jun 19, 2020 at 11:11 AM larspernorgren <larspernorgren...> wrote:
> This came up with curlews 2 months ago. Bill length among individuals of > the same species varies a great deal and much of it is gender-based. It is > common to see a flock with some bills 30% longer than others. Very tempting > to ascribe multiple IDs. > > > > Sent from my Verizon, Samsung Galaxy smartphone > > -------- Original message -------- > From: Noah Strycker <noah.strycker...> > Date: 6/19/20 10:59 AM (GMT-08:00) > To: Robert O'Brien <baro...> > Cc: obol <obol...> > Subject: [obol] Re: White-rumped vs. Semipalmated Sandpiper? > > In spring, a White-rumped Sandpiper (in breeding plumage) would have > dense, crisp lines of streaks across the breast and down the flanks, and > the base of the lower mandible would be light fleshy colored. A > White-rumped's bill should be more tapered toward the tip, and appear a > little droopy. As Bob pointed out, the structure of this bird also doesn't > fit the long-winged, drawn-out profile of a White-rumped (which is > structurally closest to Baird's, befitting those two species' long-distance > migrations). > > There is some variation in bill length/shape in Semipalmated Sandpipers > (though not as variable as Westerns); relying on bill proportions to ID > calidris sandpipers is tricky at best. > > Good birding, > Noah > > On Fri, Jun 19, 2020 at 9:09 AM Robert O'Brien <baro...> wrote: > >> Now maybe since we mostly see juvenile Semi Sands in fall in Oregon, >> perhaps juvenile Semi Sands have blunt bills >> that later get pointed as they mature? Or is this going off the deep end? >> Bob OBrien >> >> >> On Fri, Jun 19, 2020 at 9:00 AM Robert O'Brien <baro...> wrote: >> >>> Well, I dunno. That is a often-mentioned mark for White-rumped, but I >>> think this guy fits into that slot OK >>> Here is an overlay with a White-rumped from Macaulay library, sizing >>> more or less the same and lining up the eyes. >>> Has anyone ever seen a Semi Sand with a sharp bill like this in Oregon? >>> Any photos? >>> Bob OBrien >>> >>> On Fri, Jun 19, 2020 at 8:48 AM Bob Archer <rabican1...> wrote: >>> >>>> Hi: >>>> >>>> Structure is wrong for a White-rumped, they have long primaries well >>>> past tertials and the tail. >>>> >>>> Bob Archer >>>> >>>> On Fri, Jun 19, 2020 at 8:39 AM Robert O'Brien <baro...> wrote: >>>> >>>>> While looking for something else I accidentally came across this >>>>> photo, taken this month in British Columbia >>>>> https://ebird.org/checklist/S70446153 >>>>> Identified as a Semipalmated, I'd suggest a White-rumped, based upon >>>>> the narrow, sharply-pointed bill. >>>>> But, seems like I recall some discussion some time suggesting that >>>>> eastern Semipalmated have more pointed bills than the ones we get here on >>>>> the West Coast, which can usually be IDed from Western just by their blunt >>>>> bills. >>>>> No discussion of the ID in the eBird report and an easy mistake to >>>>> make, unless you looked for the rump in takeoff/flight. And since >>>>> White-rumped would not be expected, who knows? >>>>> What do people think? >>>>> Bob OBrien Carver OR >>>>> >>>>> >>>>>