golden-plovers at Arroyo Laguna


Kevin Zimmer
 

In an earlier post, Bill Bouton solicited opinions on the specific identity of the two golden-plovers (first found by Will Knowlton) that are being seen at Arroyo Laguna.

I made it up to Arroyo Laguna this morning (Sunday) to check on the golden-plovers, which, to this point, I had only seen photos of.  From looking at the various photos that others have taken, I can see why the identification of these birds is contentious.  On purely structural grounds, the birds appear to be Pacific Golden-Plovers.  The primary projection is shorter than what I would expect to see on American Golden-Plovers, and there are fewer exposed primary tips beyond the tertials The latter mark, although generally reliable/diagnostic, can be difficult to discern with anything less than excellent views, but the quality of digital photography these days is making the mark at least easier to confirm.  Primary projection beyond the tail tip is easier to see, and is usually the first thing that I go to when mulling over an unidentified golden-plover in anything other than full alternate plumage  Also, on average, Pacifics look longer legged (both above and below the "ankle") to me than Americans, and that squares with several of the photos that I have seen of the Arroyo Laguna birds.  Conversely, the plumage of both Arroyo Laguna birds (but especially that of the duller individual) is drabber (particularly less golden around the face and sides of the neck) than what I would consider typical for Pacific, especially if the birds are juveniles in fresh plumage.

However, in looking at Tom Edell's photos and Bill Bouton's photos, it is obvious that one of the two individuals is distinctly brighter and more spangled with gold on the crown and back, and that individual also has more brightly spangled (albeit with white) tertials and coverts.  That brighter individual also shows paler lores and a less patterned look to the face (this is particularly evident in one of Tom's photos), both of which, in my experience, are more suggestive of Pacific Golden.  American Goldens more often have a dusky smudge between the eye and the bill, and have a more distinctive and contrasting (usually whitish) supercilium.  The duller of the two individuals is markedly duller in plumage than any Pacific Golden that I can remember seeing, and about typical for American Golden (and even duller than many American Goldens at this season).  I will offer the caveat that although I see lots of both species in alternate plumage on their breeding grounds in Alaska, and I see lots of American Golden-Plovers in basic plumage on the wintering grounds in Brazil, it has been some years since I've seen many Pacific Goldens in anything other than alternate plumage.

I'm not suggesting that the two individuals from Arroyo Laguna are different species – in fact, I would think that highly unlikely, even given the differences in plumage between the two.  But this does serve to illustrate just how variable the plumage characters can be.  Structurally, the two birds look about the same, and both are more typical of Pacific Golden, at least as judged from the photographs.

Given all of this, I was eager to see the birds myself, so that I could base my opinions on living, moving birds rather that a handful of still photos take by others.   I had to hike 1/2 mile or more to the south of the parking area (encountering 2 elephant seals en route) before I found any plovers other than Snowy (at least 45 of them in view at one time, including 1 banded bird) or Killdeer.  As I approached a distinctly rocky point, I encountered a flock of mostly Black-bellied Plovers (ca. 20 birds), with a few Black Turnstones, and at least one Golden Plover, on the beach, but pretty directly into the sun for me.  Again, on structure, the Golden looked more like Pacific, but my views were little better than silhouettes.  Before I could maneuver to get around them and get the sun at my back, the whole flock picked up and flew north, circled 3X near the creek mouth, and then disappeared from sight.   That was about 1030 h.  I was unable to relocate them, despite searching for another hour.  So, inconclusive views as far as I was concerned, but suggestive of Pacific Golden based purely on structural characters.


Kevin Zimmer
Atascadero

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