Response to the  ¨Pluvialis¨ Plover Hotline Photo

  
Message from Bryan Dixon:  (29 Aug 2006)

 Jean and I believe we may have seen a Pacific Golden-Plover on the north side of the Antelope Island Causeway 1/4 mile east of milepost 3 on Sunday, August 27. We observed the bird from 75-100' through a Kowa scope. It had a definite golden coloration throughout the body - not gray - and its wingtips protruded just barely beyond its tail. Back feathers had golden, not white edges, though the greater coverts appeared to have some white edges. Possible it was a golden-colored Black-bellied Plover, as it looked as though it was molting out of a black coloration on its belly. Undertail coverts were decidedly not black. We've never seen Pacific Golden-Plovers before and have little experience with Black-bellied, so we're unsure how much variation there is in golden color or wingtip length. Sorry, no photos. I would appreciate hearing if anyone else noticed the bird. You can contact me at bdixon at xmission.com. Thanks. Bryan
  

From Steve Carr:  (31 Aug 2006)

So - who's going to take a stab at this plover photo? Of course, unfortunately, we can't always tell from a single picture, but there are some features to go by.
  
I don't think it's a Black-bellied Plover because of the bill shape and size, the dark cap, the wing tips appear to be a tad longer than the tail, and the general overall coloration.
  
The general appearance is of a juvenile. Some things suggesting a Pacific Golden-Plover - the heavy yellowish coloration (although the setting on the camera may affect that to some degree), the wing tip:tail appearance, the darker ear marking. Pacific's are supposed to have somewhat longer legs than American's, and these legs look quite long. Most Americans by now, both
juvenile and non-breeding adults, have a lot of whitish speckling on the back, but not much "golden," and they don't show that much yellowish wash in the cheeks (again, possibly a camera artifact). The bill might tend a little toward the American, but maybe not. I've also heard some professional Field Ornithologists say that in the fall/winter, it's often more difficult to tell an American Go-Pl from a Black-bellied Plover, than it is between the American and Pacific Go-Plovers.
  
If it's a juvenile Pacific, that would explain its inland straying (not exactly knowing where it's supposed to go). I've seen a fair number of Pacific's in winter plumage in Hawaii, and they looked a lot like this specimen.
  
--Steve Carr
  

Analysis by Stephen Peterson:  (Fri, 31 Aug 2006)

From Cliff Weisse:  (31 Aug 2006)

I'll throw my two cent's worth into this discussion because I can't resist shorebirds. This bird is not a juvenile. The black on the belly eliminates any juvenile Pluvialis plover. Since it's an adult, or first summer bird(?), it can't be a Black-bellied because it's obviously much too golden in coloration, in addition to the structural points already mentioned. The most important field mark for seperating American from Pacific Golden Plover is the primary projection (the distance the primaries extend beyond the tertials) as well as the number of primary tips visible beyond the tertials. On this individual you can't make out the primary tips to count how many are visible but the projection does look short for an American. The bill looks better for American.
Guess I'm not willing to go out on a limb and call this a Pacific but I'm not willing to say it is not one either. Very interesting bird.

Cliff
  

Analysis by Mark Stackhouse:  (Fri, 1 Sep 2006)

O.K., I think I'm ready to wade into this one (not too shy about it, but wanted to do a little review of the literature first). First, Cliff is right, it's definitely an adult bird - the black remaining on the belly means it's been through at least one breeding season. This is perhaps unfortunate, as the i.d. might be a bit easier if it were a juvenile.

As far as what type of plover, I think we can safely say it's not a Black-bellied, due to the small, thin bill and overall brightness of the plumage (remember that it's an adult, and all adult Black-bellied
Plovers would be much grayer).

Now, which of the Golden-Plovers? My first impression was American (and I don't think that it was just because that would be more likely). Most of what I can see, and was able to confirm in my "literature review" seems to support this first impression.

The nature of the photograph makes this i.d. even more challenging. Some of the conventional field marks, wing-tail length, primary extension and number of exposed primary tips cannot be seen well enough in this picture. Also, the bright lighting makes it a bit hard to judge subtle colors, such as how yellow/gold the spots on the back appear. The angle and posture of the bird makes judging the overall length, uprightness of the stance and leg length (all things I've used to pick likely Pacifics out of flocks) difficult.

So what does this leave us? Not much, but maybe just enough.

First, there are a couple of structural features which we can see (I always like thing that are independent of plumage/lighting). The bill seems very thin and short - both good for American, as most Pacifics have a somewhat thicker, and especially longer, bill. Also, Pacifics usually look somewhat larger headed, and this bird's head looks rather small. Nothing definitive in this, but suggestive.

The plumage characters are complicated by the fact that the bird is still molting. However, both Golden-Plovers start molting the head and facial feathers quite early, sometimes even while still incubating, so the head of this bird is probably fully in basic (non-breeding) plumage. There are several plumage characters on the head that can be useful, and they all suggest American in this individual. First, the supercillium is very white (usually a bit buffier in winter Pacific), and, more importantly, is wider past the eye and continues towards the nape rather than sharply bending down and around the auriculars. The effect of this is to make the dark stripe from the crown down the nape very narrow, whereas on the Pacific the dark patch on the nape is wider. This field mark is well illustrated and described in the new shorebirds guide by Michael O'Brien, et. al. Also on the head, the "loral smudge" in front of the eye and the auriculars behind the eye both look quite dark (though this might partly be because the face is in shadow), which is better for American.

Another good plumage feature in basic-plumaged Golden-Plovers is the brightness of the back, probably due to larger yellow spots on the Pacific, though they may be yellower in some individuals as well. Regardless, Pacifics usually look brighter/yellower than Americans. This is hard to judge on the bird in the photo because of the partial molt and the harsh lighting. However, the new feathers that have come in look to me to be rather dull and unspotted - which again suggests American.

Perhaps the strongest evidence that this is an American has to do with the molt sequence and timing. In general, the Pacific completes its pre-basic molt a little sooner than American, and the sequencing of parts of the body is slightly different. In particular, Pacific Golden-Plovers molt their underparts before their back, so that in many individuals in September the belly is fully white while the back
retains breeding plumage until October. This bird is molting both the back and the belly at the same time, as in American.

It's not as clean an I.d. as most of us would like (including me), but I'm sticking with my first impression that this is an American Golden-Plover.

Good birding!
Mark Stackhouse
  

From Kris Purdy:  (Fri, 2 Sep 2006)

I'm in agreement with the party of birders that observed the Pluvialis plover on Antelope Island Causeway this afternoon--that it's a PACIFIC GOLDEN-PLOVER. Thanks to Buck and Cindy Russell for refinding the bird and to Susan Saffle for calling me.

I visited the causeway later this afternoon and observed the bird for 2 1/2 hours. Paul Higgins was there in advance and took many superb photographs.

The bird is definitely an adult and has lots of black splotches on the lower breast and belly and a few spots aft of the legs. Of course, that also indicates the molt is incomplete. I noted several area of worn feathers, including one tertial, the wing coverts below the scaps, and a few scapular and back feathers sprinkled among many more that looked fresh. I believe the remaining flight feathers are also worn because they're a paler shade of brown than the base color of the scapular and back feathers. The notches on those feathers were orange or deep buff against dark brown centers.

The wingtip projection past the tail is short--perhaps less than 1/4 inch. More importantly, the tertials appeared as long as the tip of the tail. My best look at the primary tips projecting past the longest tertial showed two. But this was very difficult to ascertain. I had excellent light conditions and optics, but the color of the tips is uniform and they blended together.

By the time I left around 6 pm the bird was not quite a tenth of a mile west of mile marker 5, north side of the causeway, where the rocky/weedy slope of the causeway meets the mudflat. The distance from the pavement was 90 feet according to the distance meter in Paul's lens. The bird likes to rest next to clumps of vegetation and several times was barely visible on the north side of a strip of ragweed. We would not have known it was there had we not seen it walk there.

Prior to my arrival, Paul saw the bird farther out and it difficult to observe at that distance. Thank goodness it came in about as close as possible to have its picture taken.

Thanks to all who reported and have participated in the discussion. I was much better prepared to observe the plover carefully due to your contributions. As you know from the analyses this past week, the ID challenges between the Pacific and American Golden-plovers is very difficult. Take with you a healthy dose of skepticism and identify the bird to your own satisfaction. All opinions welcome, including the ones different than mine :^D.

Kris
 

From Joel Beyer:  (Fri, 2 Sep 2006)

Kathy and I arrived at the Causeway this evening and Paul Higgins kindly pointed out the golden-plover. After 2 hours of intense study, we're leaning toward Pacific. We concur with Kristin's description of the body and tail. We both managed to get a decent look at the primary tips extending beyond the tertials. Kathy counted three, as did I, only I think the longest primary may actually have been two nearly equal in length (very hard to discern). The bill appeared thick, particularly at the base, and fairly long. The entire facial area was yellowish, with a buffy supercillium. The area around the eye was pale, and we observed a very distinct postocular spot separate from the eye. The undertail coverts were an immaculate white. The leg length may favor American - the tibia appeared short, bringing the knee closer to the body rather than midway between the body and ground.

Hopefully Paul's photos will help resolve this extremely tricky ID.

Joel
   

From Rick Fridell:  (Fri, 4 Sep 2006)

Hello Everyone,
Outstanding photos by Paul Higgins. This is an intriguing bird, and at first look I was almost sold on thinking it's an adult Pacific Golden-Plover.  However.... Outside of typical breeding or (even non-breeding) plumages, distinguishing these species should be based on structural / proportional differences (rather than plumage differences). Therefore, I'm basing the following on looking at Paul's photos for clues on relative proportions.

The difference in wing-length between the two species has been well-discussed... American GP has relatively long wings projecting well beyond the tip of tail and the Pacific GP has proportionally shorter wings, projecting just past the tip of tail. In addition, American GP has a
longer primary projection with three to four primaries typically visible beyond the longest tertial. Another key factor in distinguishing these species is the length of the tertials relative to the tail tip; obviously shorter in American GP and with tertials of the same length or projecting beyond
the tail in Pacific.

So looking at Paul's photos for these clues, reveals the primaries extending just beyond the tip of the tail (photos 1,4,5,6 - a point leaning towards Pacific GP) but the tertials are clearly shorter than the tail (photos 1,4,5,6,7 - a point leaning towards to American GP) ???? (And these
characteristics are supposed to be definitive!). Gauging actual primary projection is tough from these photos, but looking closely reveals both the primaries and the tertials to be very WORN. I think feather wear may be reason for the discrepancy in these characteristics. First check out
the last photo of the obviously very worn primary tips, then check out the outline of the right wing in Paul's third photo (of the plover with its wings spread). The wing outline clearly shows worn feathers, shortening the tips of the outer primaries, and overall wing length. I believe this
feather wear accounts for the small difference between wing and tail tips, and artificially (temporarily?) makes this trait appear to favor a Pacific GP.

Of course I haven't actually seen the bird, and perhaps one could argue the tertials or even the tail are proportionally worn. The tertials do show a lot of wear, particularly in photos 6 and 7, but even with this wear they appear clearly shorter than the tail.

As to other structural differences, Pacific GP have a proportionally longer bill and legs than American GP. These characteristics are hard to distinguish on a lone bird, but may be helpful in direct comparisons.  The long legs of a Pacific GP typically project beyond the tail in flight,
so this may be something to watch for if this bird sticks around. Also the call notes of the two species are diagnostic, with a rising second syllable in Pacific GP (opposite in American).

Very nice descriptions and photos from the Northern Birders. Well done. Keep the observations and discussions going. You've inspired me to get out of the house and go birding this afternoon.

Best Regards,

Rick Fridell
Hurricane, UT
  

From Ken Behrens:  (Fri, 4 Sep 2006)

From Mark Stackhouse:  (Fri, 4 Sep 2006)

David Wheeler and I went out to the causeway today and located the Pacific Golden-Plover without trouble in the previously reported location. Seeing the bird in the field, if I were on the west coast, I wouldn't hesitate to call it a Pacific Golden-Plover. That is good, since I had already reached the same conclusion after reviewing Paul's excellent photos. I also posted a query to the i.d. frontiers group, and (I think the first time I've seen this happen with that group)
received a unanimous reply from ten experts that this is a Pacific Golden-Plover. For the record, I'm certain that this is a different bird than the one posted last week with the photo by Keith Evans - look at the difference in the facial markings and the partially molted back as opposed to the Higgins bird which has its back still in breeding plumage.

There are many features visible in Paul's photos that favor Pacific Golden-Plover, several of which have been pointed out in other posts or which you could infer by reading my earlier post on the Evans bird. I was impressed by how worn the outer primaries are, and wondered
whether the short primary extension could just be an artifact of wear. The worn outer primaries are decisive in this i.d., but not for that reason. Although there are a number of coloration features that favor Pacific, including the facial markings and spotting on the back (two pairs of gold spots on the edge of each of the mantle feathers as opposed to only one pair in breeding plumaged American), many of you know that I'm not a big fan of coloration in tough identification problems like this. Structural features, and things like molt sequence, are much more secure as field marks.

If you look at the third of Paul's photos (the one with the wings spread), you can see that the worn outer primaries contrast with the inner primaries, which are fresh, even-tipped and unworn. The outer-most of these fresh inner primaries is obviously longer than the next outer primary, which is worn (if it they were fresh each primary would be a little longer as you move out the wing). This bird appears to be about halfway through molting its primaries. Neither the Pacific
nor the American Golden-Plovers molt their flight feathers during migration. However, the Pacific starts its molt on the breeding grounds, and finishes on the winter grounds after the migration. Americans don't start molting their flight feathers until they reach the winter grounds. A recent paper by Al Jaramillo states that, "...an autumn golden-plover in wing molt in California, and probably anywhere in North America, is almost certainly a Pacific." Because of the severe wear on the outer primaries, this bird is probably a second-year bird, since these primaries would be from the juvenile plumage acquired last summer rather than a pre-basic molt last winter and thus older by several months.

An interesting bird and a great, well-documented, state-first record.

Good birding!

Mark Stackhouse
  

Comments from ID Frontiers sent in by Tim Avery:

Kevin Karlson (one of the authors of the new shorebird guide) posted a little about the PGPL being seen at the causeway, and I think it may be of interest to everyone. Both his emails are pasted below:  [Tim Avery]

I have enjoyed all the discussion related to plumage of the Utah Pacific Golden Plover that was shared by a number of shorebird experts, but nobody other than Lee Evans referred to the very obvious structural differences between Pacific Golden and American Golden Plover. Without
even looking at plumage, it took about two seconds of seeing the first photo to realize that this was not an American Golden Plover. If anyone spends some time studying the shape and structure of these two species, a good number of questionable individual birds may be identified
without ever looking at feathers.  For Pacific Golden Plover (compared to American Golden), the combination of a blocky head, large bill and chunky, rounded body gives this species a profile similar to Black-bellied Plover rather than AGPL. American Golden has a pigeon-like head in shape, with a smaller, thinner bill. This smaller head and thinner bill often looks proportionally small in relation to its body than that of PGPL. The shorter rear quarters and primaries of PGPL further adds to a more rounded, shorter body profile than that of AGPL. In some individuals, such as this one, the very long legs, especially the tibia, creates a lanky appearance to the structure of the bird, which is not seen in AGPL. The combination of all these factors often seals the ID of a questionable bird within seconds. Of course, feather analysis will
further solidify the ID, and allow for aging of most birds.

Sorry for this second posting, but I forgot to whole-heartedly agree with Killian that the other bird in question from Utah birds photographed a week earlier is the same individual as the bird shown in this post. You don't need a close-up photo to see the same obvious structural characters of PGPL, especially the very long legs, of the earlier bird. Sometimes a more distant photo allows for better analysis of a birds overall structure anyway. Another interesting point is that the observer stated that "Attached is not a very good photo, but I'm trying to make it an American Golden instead of a Black-bellied juvenile." In my previous post, I mentioned that the structure of PGPL is often more similar to BBPL than AGPL, which caused Keith Evans to
struggle with the ID. When you see a problematic Pluvialis plover, see if it resembles BBPL in overall shape, with a blocky head and bulky, rounded, somewhat shorter body shape, with noticeably long legs. If it does, give it more scrutiny.

Kevin Karlson
  
 

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