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Index of Subjects Ian, I have been looking at "Shorebirds, An Identification Guide to the Waders of the World" Hayman/Marchant/Prater. The illustrations and text support Common Ringed Plover. From my perspective coming here from the UK where Common RP is common, SP Plover appears smaller and slimmer (less bulky) reminiscent of Little Ringed Plover. I find this size difference striking at times. Dennis On 1-Oct-09, at 3:57 PM, iamclar@dal.ca wrote: > All: > > Here's a copy of a note I sent to the advanced i.d. site at > birdwg01, Tricky > business, but I feel that it was indeed a Common Ringed Plover. > > It is good that Dave Brown gave access to the image of an > interesting small > plover photographed [by Nicolass Honig] Sept. 4 near Halifax, Nova > Scotia. It > came to my attention after Allan and Cathy Murrant saw the photo and > pointed > out features of Common Ringed (CORP) rather than Semipalmated Plover > (SEPL) - > lack of visible orbital ring and broad breast band. They also posted > the image, > along with great shots of a Eurasian Whimbrel in Sydney, NS, in > early Sept. > > <http://www.capebretonbirds.ca/rarebird.html> > > With Dave Brown, I have been agonizing over it since, and both of us > are puzzled > by the lack of response on this forum. Is it considered too > obviously one > species or the other? I have checked numerous images, particular > from Google > and Vireo, of fall-migrant adults (July-November) and they sure > address some > views on distinctions. > > 1. Widths, shapes and sizes of breast band and all dark head patches > on both > species vary individually, and highly with posture (a warning in > some sources). > Few SEPL show as evenly broad breast band when expanded as the NS > bird. Few > CRPL have a strongly convex lower border of the auricular patch, and > rarely so > far back as on the NS bird, but some do(depending on posture?), > whereas most > SEPL have this shape. > > 2. White patches are quite variable. The white frons can extend to > the eye in > both species, or there can be a dark intervening area. One nice > image from > Iceland shows a July adult with a very broad dark area between white > frons and > eye. Shape and extent of the white supercilium also varies greatly > in both > species, and behind the eye can extend below the upper border of the > eye in > both, though more so in some SEPL. > > 3. True length and height of bill (see Pyle's Id Guide . . . on > this) are of > little use, but SEPL almost always shows a slight "dip" in the culmen, > imparting its oft-mentioned slightly bulbous tip. The CRPL culmen > seems always > straight until near the tip, making it seem longer and thinner (head > on images > seem to show the CRPL bil as more sharply pointed). The NS bird > seems good on > bill shape for CRPL. > > 4. The tone of back and wing plumage of most (but not all) CRPL is > distinctly > paler and grayer, but a few SEPL can be quite grayish. There is some > possibility of confusion here from the use in photo guides of images > of darker, > browner _tundrae_ from Eurasia and AK. The expected _hiaticula_ > from Greenland > and Nunavut is sometimes separated as a browner subspecies, but > that's also > said to be dubious. The NS bird is a little problematic, as its back > is > strongly shaded amd its wings and flanks obliquely lit. But, a zoom > of the > image shows a distinct paler gray cast to the better-lit scaps and > coverts > > 6. The pale orbital ring (distinctly yellow in fall-migrating > adults) of SEPL > is a most salient feature, surely, and is clear on all decently > sharp images, > even when ill-lit. The dark brownish or dark brownish orange orbital > ring of > CRPL is obscure at best and completely invisible on most well-lit > CRPL images. > The light on the BNS bird is oblique on the head, but it is sharp, > and zooming > reveals no hint of pale orbital ring, especially at the reasonably > well-lit > front of the eye > > Finally, although CRPL and SEPL are rated as good species, and > although Smith > (Ibis, 1969, 111: 177-188) made some dubious observations on mixed > pairs > producing Mendelian ratios of morphology of each species, > interbreeding may > indeed occur in n. Nunavut (especially with global warming?). How > would one > pick out a hybrid? > > Cheers, Ian McLaren > > Ian A. McLaren > Biology Department > Dalhousie University > Halifax, NS Canada B3H 4J1 > >
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