Friday, 12 October 2012

American Golden Plover and Grey Plover

This is a series of photographs that we took at MZUSP. We noticed that there was a lot of confusion about separating these two species in Brazil, so we set about writing a basic ID guide for Brazil. It never got published but the thought was there.

Most people in Brazil (and probably elsewhere too), rely on seeing the axilliary feathers to clinch the ID of a single Pluvialis plover on the beach, black in Grey Plover and grey in American Golden Plover.

However, if the bird doesn't fly it is still possible to make a firm ID of the bird given good views. It is not good bird craft to cause a bird to fly just to ID it, especially if it is a migrant.

With a single bird, comparison of the bill is not easy, but this photo shows how much bulkier the bill of Grey Plover (right) is than American Golden. Also the more capped appearance of American Golden can be seen here as the supercilium in Grey is not so well defined.
American Golden Plover Pluvialis dominica (left) & Grey Plover Pluvialis squatarola
© MZUSP
 Grey Plover Pluvialis squatarola

American Golden Plover Pluvialis dominica


Another anatomical difference can sometimes be hard to see in the field, especially if the birds are feeding in soft mud or sand. Grey Plover is the only Pluvialis plover to have a hind toe. It is very small but should be visible with good views.
Grey Plover Pluvialis squatarola
© MZUSP


American Golden Plover Pluvialis dominica
© MZUSP
 The other, and perhaps easier, way to tell them apart is to look at the wing tips, count the number of primaries visible beyond the longest tertial (primary extension)

Grey Plover Pluvialis squatarola 3 visible primaries
© MZUSP
and see where the wing tip falls in relation to the tail tip.
In this photo you can see that the bird was undergoing moult when it was collected. The second longest tertial on the right wing is very worn but its equivalent on the left wing is new and the longest tertial is missing. This is a point to note when observing primary extension, look at both wings if possible as moult can affect this feature and can lead to mistakes being made.
© MZUSP
American Golden Plover Pluvialis dominica 4 visible primaries
© MZUSP
 ---
The wing tips on American Golden Plover fall beyond the tail tip giving the bird a very pointed look to its back end.
© MZUSP
The other feature that can be hard to tell depending on how the bird is holding its feathers, is the jizz of the bird. grey is bigger and heavier, more stout and has a blunter back end. American Golden plover has a much more dainty appearance.
Grey Plover Pluvialis squatarola
American Golden Plover Pluvialis dominica

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