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.

https://search.macaulaylibrary.org/catalog?bmo=8&taxonCode=semsan&mr=MCUSTOM&region=Oregon,%20United%20States%20(US)&emo=9&regionCode=US-OR&q=Semipalmated%20Sandpiper%20-%20Calidris%20pusilla

There is an especially nice photo in comparison with Western by Phil
Pickering here.
https://ebird.org/checklist/S59670500#flag-176578101&_ga=2.251674441.177613398.1592550564-824734375.1590261844
(no white-rumps are involved here, of course). The middle Western is very
likely a female.


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.

Finally, if you look at this report
https://ebird.org/checklist/S37336776#flag-60179801&_ga=2.247430084.177613398.1592550564-824734375.1590261844
you'll see an alleged White-rump quite similar to the bird in question.
But.....it does show a tiny amount of pale coloration at the base of the
bill. And the following photo in that report is of a Semi Sand for
comparison.

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
>>>>>
>>>>>
>>>>>

 
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