Folks,
Thanks first of all to all those from Australia, Ireland, UK and USA for their
inputs into the identification process. In this process I have attempted to
identify the bird beyond reasonable doubt - I am unable to do so for either AGP
or PGP, despite generally very good photos, field notes and a sizeable review
of the literature. I will not be submitting to BARC.
I won't go through the process ad nauseam but thought it would be worthwhile
reviewing what were for me the key points, learnings and some pointers for
birders/researchers. I have summarised the id points below (NDF - not a
definitive fieldmark) and my estimate of what probability of either species
Size
Pacific American
Same length as accompanying PGP (American generally bigger) 70%
30%
Shape
More horizonal stance, slightly more bullchested, but seemed slimmer 80%
20%
Wing length
10% longer carpal to primary tip
30% 70%
Primary projection beyond tail
75% of bill length - therefore 15mm to 21mm. Outside ranges given
20% 80%
(but Oscar Johnson believes more fieldwork is required to confirm extremes)
Tertials to primaries
The relationship was unclear as many tertial were missing or very worn
0% 0%
Tertials to tail
The relationship was unclear as many tertial were missing or very worn
0% 0%
Bill length
- -
Same length (large overlap) (NDF)
Head size (NDF)
- -
Same (large overlap)
Bill backward over eye (NDF)
- -
Much the same (large overlap)
Leg length
Shorter leg. Slight projection beyond tail v all of toes (NDF)
40% 60%
Plumage
Molting. Much greyer than PGP, with very little gold spangling (NDF).
50% 50%
Oscar Johnson has seem many similar birds this month in Hawaii
______________
40% 45%
Pacific Golden Plover? Reasonable doubt exists
American Golden Plover? Reasonable doubt exists
Suggestions for birders
1. Extensive field notes, photographs and sketches required particularly
tertial, primary, tail relationships
2. Suspect grey molting birds are (in my view) highly unlikely to be clearly
identified one way or the other in the field, unless backed up by a faecal
sample for later DNA analysis (I initially thought this was a daft suggestion
but having observed Grey and Pacific this week it is realistic - I now carry
small sample bags in case)
3. See one from November to March!
Suggestions for researchers
1. Investigate relationship between primary tip to carpal measurement and
overall length on PGP and AGP (this can be photographed in the field)
2. Detailed comparison of autumn molt birds
Cheers,
Graham Buchan
==============================www.birding-aus.org
birding-aus.blogspot.com
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