Friday, August 21, 2015

Another Fun Shorebird Challenge! - 21 Aug 2015

Semipalmated Sandpiper
Friday afternoon / early evening brought gorgeous skies and low winds, so I headed out to Pt. Mouillee to check on shorebirds. Parking at Mouillee Creek I made my way along the Middle Causeway toward the Banana Unit and enjoyed a nice leisurely evening of birding.

A pair of Northern Harriers floated lazily over the Long Pond Unit and tussled with each as they crossed paths. Large flocks of Red-winged Blackbirds were flushing from either side of the causeway as I rode, but no Yellow-headed Blackbirds were among them.

I stopped at the SW corner of the Vermet Unit and decided to hike out onto the peninsula to get some pics of the Caspian Terns roosting at its point. Five Snowy Egrets were foraging nearby, and offered only distant pics before they flushed at my approach.

The Caspian Terns were noisy, and circled closely with little regard for my presence.

I continued on to Cell 3 and was surprised to see roosting birds way off in the southeast corner. As I approached I realized that, although the north end of the cell was under water, the south end had mud flats! As I scoped the area I found a Black-bellied Plover, and hundreds of Semipalmated Sandpipers. I rode around to the south end managed to find a few Semipalms near shore, and six Short-billed Dowitchers along the shoreline.

An American Goldfinch was posing nicely just a few feet away, so I took a few digiscoped images of the bird in the early evening sunlight.

A single juvenile Lesser Yellowlegs was nearby, so I followed it awhile before turning my attention to the Semipalmated Sandpipers.

The Semipalmated Sandpipers were scattered all over the south end of Cell 3, taking advantage of the fresh, wet mud from recent dredge-dumping. Most were fresh juveniles with clean, white fringes, streaked foreheads, and a blush for chest markings.

One bird got my attention, however. As it foraged among its peers I noticed that it appeared slightly larger, longer-winged, and longer-billed. Western Sandpiper? White-rumped Sandpiper? Baird's Sandpiper? It was going to take some breaking down. Compare the bird at left with the Semipalm at top.  Bill is longer, and slightly decurved? Wing projection appears long, suggestive of a Western Sandpiper juvenile. However, the back appears scalloped, suggestive of a juvenile Baird's. But the throat doesn't quite show the distinct, buffy necklace one might find from a Baird's juvenile. The supercilium (eye stripe) is pretty bold and suggestive of a White-rumped Sandpipers. So, can one photo give us the answer?

I decided to pose the question to the I Shorebirds Group on Facebook, and as expected, got the complete range of answers from other shorebird aficionados.

Juv Semipalm for comparison

Although I had a few dissenting opinions, my gut feeling was that this is a juvenile Semipalmated Sandpiper despite the bill, wings, and supercilium appearing exaggerated. Wing coloration (brown-black on gray) is similar to the other Semipalms. Streaking on head is similar, as well. Throat coloration is not distinct (as in Baird's), and not fine-streaked as one might find in a White-rump.

Luckily, I remembered a response I got last year to a similar bird from Kevin Karlson, author of The Shorebird Guide, and he provided some interesting comments regarding Semipalmated Sandpiper identification. Basically, he mentioned that Semipalms show a wide variation in bill length and wing projection, with females typically having longer bills and wings. They can also appear larger, as in the case of this bird. Kevin was gracious enough to respond to this bird, and offered the following:

This is clearly a case of how a single photo can show a bird in a pose that is in a misleading instead of helpful posture, like the first shot. Glad for the second photo of this juvenile female Semipalmated Sandpiper. Although it may resemble a Baird's or White-rumped due to the long body and wings, some large female Semis can have very long rear bodies and wings, but the wing/tail ratio is spot on for a Semi and definitely not a Baird's (whose wings extend well past the folded tail), and although some White-rumps can have wings that just reach the tail tip (usually males), their plumage as juveniles would be way different that this bird, and the bill shape is wrong for both Baird's and White-rumped. I could go on and on about the differences between this bird and the other three, but it is clearly a Semi, and the space here is limited. Not a Western for so many reasons, both structurally and plumage, but the bill is too blunt tipped, the plumage is wrong for Western (no rust scapular line), and the body structure is too evenly weight distributed for Western, which would show a bigger, blockier head; front heavy and chest/shoulder heavy weight distribution. The dark cap that contrasts with a paler nape is also a juv Semi feature, with Western showing a grayish cap with dark streaks and a mostly grayish nape. Good comments and discussion. Sorry, Baird's juv would have a finely streaked upper breast that is well defined, and a bill that is not as thick at the base and more fine tipped than this bird.

Thanks again, Mr. K!

I continued to scan the east shoreline of Cell 3 but failed to see anything other than Least and Semipalmated Sandpipers. I did spot a Bonaparte's Gull in the NE corner of Cell 3, and hoped for a while that it might be a Franklin's, Laughing, or Little Gull (negative on all points).

An American White Pelican was in the south end of Cell 4 and provided a nice photo from the bike.

The rest of the ride would be uneventful until I flushed a Willet in the Long Pond Unit as I rode back to the car.


Roger Eriksson said...

Great shorebird challenge - my first thought was Baird's because of the wing extensions but then upon closer scrutiny other possibilities occurred.Kevin answered all the variables. Thanks Jerry for your wonderful blogs.

Debra Wolf said...

Thank you for sharing these very fine ID points, Jerry. I am trying to get better acquainted with what is to me a very confusing group of birds. A very helpful and enlightening discussion!

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