9 May 2010
Antelope Island Causeway
Davis County, Utah
(Clip for an E-mails from Glenda Cotter, 9 May 2010)
... I may have a few not very good
photos of the mystery plover. I took them Saturday afternoon around 3:30
p.m... Although I realized I was seeing something odd when I took the
pictures, I didn't have time to sit and puzzle and thought I'd look at the
photos when I got home, assuming it was merely a weirdly molted BBPL. I'd
totally forgotten about the bird by the time I saw Jack and the two Bobs
further east on the causeway or I'd have mentioned it to them. Totally
forgotten it, actually, until I saw today's posts...The "landscape" photo
shows the bird in relation to a Black-bellied Plover.
Glenda Cotter
(Clip for an E-mails from Dave Hanscom, 9 May 2010)
...At mile marker 4, amidst a few hundred Black-bellied Plovers, we found
a Red Knot, a Dunlin, and a bird that Bob thought might be a Mountain
Plover. I told him he was crazy, but I must admit that he almost had
me convinced. Robert's email makes me wonder if I'm the one who's crazy.
(Some people would say that we both are, but that's another issue.)
When I found the bird, I thought it was a Pectoral Sandpiper, but with
Bob's higher powered scope it was obviously something else. It had a short
dark blunt bill like a plover, was noticeably smaller than the
Black-bellies nearby, had a brown back with a scaly pattern, light colored
legs, very light belly, and an upper breast that was streaky on the sides
and white in the middle. The brown on the chest didn't come down any where
near as far as a Pectoral.
The closest thing we could find in Sibley was an immature Mountain Plover.
I just looked through my National Geographic, and that was the only bird
that looked like what we saw. Would it be possible for a first year bird
to still be in last fall's plumage?...
Dave Hanscom
(Clip for an E-mails from Robert Williams, 9 May 2010)
On Sun, 9 May 2010, Robert Williams wrote:
had a good day though i missed the turn stone, b&w warbler and
waterthrush i did find several good things about 5 sanderlings 1 dunlin
maybe 10 red knots semipalmated sandpipers, least sandpipers, and of
most note was the mountain plover seems like a weird place for one
i was quite surprised about but cant complain i also was able to get
some poor looks at the grass hopper sparrows i heard maybe 3-4 individuals
and saw one.
(E-mails from Robert Williams, 12 May 2010)
Since the ID question still seems to be active behind the scenes, let me
throw out some ID observations about the bird I saw (which I think is the
same bird in the photos, though I can't be 100% certain):
AGP = American golden-plover
BBP = Black-bellied plover
EGP = European golden-plover
GSP = Greater sand-plover
MP = Mountain plover
PGP = Pacific golden-plover
Size: Very fortunately the bird I saw was very close to the road and very
close to a Black-bellied plover (like 2 feet). The two birds were
identical in size. Black-bellied plovers are 10.75 - 12 inches long.
Mountain plovers are 8.5 - 9.5 inches long (10% smaller). The Greater
Sand-Plovers range between 7.5 - 10 in long. Other plovers not mentioned
but which are in contention are the other Pluvialis plovers: AGP ranges
9.5 - 11.25; PGP ranges 9.25 - 10.5 in; EGP = 10.5 - 11.5.
Tail: The tail on the plover I saw was pure white with many thin black
bars. That eliminates both MP and GSP right there, as neither of those has
a barred tail. The other Pluvialis plovers also suffer in this comparison
because they often have buffy or outright rufousy tails in most plumages.
Body Shape: This plover had the body shape (once again exactly) of the BBP
next to it. The GSP has an entirely different shape, with a shorter neck
and blockier head, less plump in appearance -- more like a Charadrius than
a Pluvialis. This was very evident in the birds I saw in Thailand and the
photos I've looked at since. The one thing that was different about this
bird was that it extended its neck more often than the BBP next to it,
giving it a long-necked appearance. But that was a behavior difference,
albeit fairly consistent. When it unstretched, it's shape matched the BBP
next to it again. There were other BBPs in the area which extended their
necks as well, on/off.
Bill Shape: The bill shape and length were also a perfect match to the BBP
next to it, whereas a GSP has a proportionally larger & longer bill (more
like a Wilson's plover). The EGP can also be eliminated because it has a
more petit bill (especially narrower near tip), the AGP, though less so,
also has a more petit, slender bill. The difference is more subtle with
the PGP, but I thought this bird's bill was too robust. The MP also
usually has a more petit bill than the bird I saw.
Wing Extensions: The bird I saw had primaries which extended to but not
much beyond the tail when folded. That is consistent with BBP, GSP, and
maybe EGP, but eliminates AGP and probably PGP. Sorry, I did not note
comparison to the tertials, which many experts like to expound upon. Lazy,
pure and simple.
Color of Back & Breast: These are less trustworthy, more variable traits,
so I pay them less heed. I think any of the species in question could fit
these, at the fringes of plumage possibility, but don't get a truly
satisfying match for any except perhaps MP.
So,
- Mountain plover: eliminated by tail barring, size
- American golden-plover: eliminated by primary projections, bill shape
- European golden-plover: eliminated by bill shape
- Greater sand-plover: eliminated by tail barring, shape, size
- Pacific golden-plover: eliminated by a preponderance (no one thing) of
many things (tail color, primary extensions, size, bill shape)
+ Black-bellied plover: only bird left standing
These are my thoughts. Many of these observations can only be applied with
certainty to the bird I saw, but some, like shape, can be applied to the
photos as well.
In closing, I am aware of no records (in my unofficial data base, which
includes even sightings rejected/unjudged by the Committee) of EGP or GSP
in Utah, only about 2-3 on mudflats of MP (which is described in
literature as staying on fields & other dry areas, even during migration).
Though there may have been some, I saw no AGP there, but there were
thousands of BBPs, providing a much higher likelihood of an odd-plumaged
bird from that species than any of the other species being considered. My
guess is the bird in question was a Black-bellied plover.
I'll be interested to see if other photos show up that demote all this
analysis to an elaborate fiction based on a different bird,
David
Photos
by Glenda Cotter
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