This is my first time posting. I am birding in Singapore and recently, on 12/12/09, I photographed a golden plover that is slightly different from the rest.
It had a black and white plumage with some small gold spots on the scapulars, obvious white supercilium, grey cap and very long primaries.
Pacific golden plover is the only golden plover found in Singapore and in the region since the split occured, so the american and european golden plovers are clearly impossible to be found here. Regardless of its plumage as seen in the photos, it is clearly a pgp - no doubt (see http://www.birdforum.net/showthread....+golden+plover)
But, I am still trying to find some explanation about this plumage. Reading all the past discussions about the confusion between the pacific and american plovers have put forth some possible answers that I am interested to verify.
First explanation: Birds born in different parts of the northern hemisphere have different plumage difference. I read once that the pgps from east Siberia has longer wings than those born across the pacific. This explains the disparity between the length of the primaries projection. Still, the black-and-white plumage is not explained, so there is a need for a second explanation.
Second explanation: Different rate of moulting. Moulting schedule is always mention when separating the golden plovers sp but I feel that it is possible to use here. This odd-looking black-and-white bird has moulted into a non-breeding bird of a rare extreme plumage. Usually, pgp's non-breeding plumage has a yellowish outlook but with a whitish supercilium because of golden spots on the tertials and coverts, in addition to the scapulars. In this case, this bird preferred a less golden plumage. This explanation of a preference for a different plumage is, in my opinion, very likely although the possibility of a early and rapid moulting is rather peculiar. (Note the fresh tertials and coverts as compared to the nearby pgp)
Third Explanation: Contrary to the second, the tertials are not fresh but simply not worn or still growing. Overstaying plovers are possible for pgp but as rare as a spoon-billed sandpiper visiting Singapore. This explains why the tertials does not cover much of the primaries and suggests an alternative explanation to the peculiar case of rapid moulting without eliminating the hypothesis of plumage preference.
Fourth Explanation: Instead of "finding fault" with the bird, analysing the photo suggests that the bird is not exactly in a single plane parallel to the the bino/camera lens. Simply, the bird is tilted. Long primaries is in fact short and short tertials are in fact long. I am not sure of any method to compensate on
the tilt to get a more accurate view of the proportions. A more extreme reason, my camera and bino are too lousy to capture the subtle buff wash. Additionally, the effect of the camera on the bird's psychology may affect the bird's appearance. White Canon lens is too conspicuous and its user too intimidating. If I am the tired bird, I would try to look shorter ,smaller and less obvious by folding my wings and slouching my back. I can't really bend my tail, so just point it down, giving longish look.
Combining this 4 explanations, I would like to propose a view regarding separating the non-breeding pgp from the non-breeding agp. If you are birding in Asia and Australia, there is only pgp. If you are birding in east coast of America and South America, there is only american golden plover. If you bird in areas that is within the overlap of the range of these two species (e.g. Europe/Middle east), then the bird can only be id as golden plover, very much like the pintail and swinhoe snipes, non-breeding dunlin and curlew sandpiper and non-breeding little and red-necked stints.
My rationale for this view is the following. Primaries projection and the number of exposed primaries are hard to verify in the field and in photos but diagnostic features for use to identify birds in hand because of reasons like position of the bird in the photo, intra-species variation in moulting schedules, plumage preference and the posture of the bird. Other subjective features like bill length, tail projection from tertials, ear spot, plumage colour, overall appearance, feather pattern, leg length, wing length,... can be seen in pgp and agp. The possible permutations of the features are bound to confuse and distort the id. Having more matching features does not indicate a clearer id, much less lacking one of the subjective features.
Disclaimer: My view is base on my limited knowledge of the differences of the birds born in different breeding ground. Additionally, I, myself, do not believe that there are birds that can't be id in the field, so if any of you have a possible diagnostic feature or would like to suggest a diagnostic combination of features, please share with me. Lastly, I am a "deaf" birder, having problem identifying calling birds, so my view may be flawed in this aspect. Form the many discussions, both in surfbird and BF, I find that agp and pgp have distinct calls but they also have similar calls, so depending on their emotion and preference, calls can be rather subjective as a agp in a pgp flock may call like a pgp. (Nobody likes to be ignored and I think most birds have sufficient intelligence to make subtle adjustments to their call to be heard, be it loud/soft, fast/slow, abrupt ending...)
Pls feel free to comment on the long-winged pgp and my ridiculous explanations.