george_vaughan 的鑑定

As with any presumed hybrid to not undergo DNA testing, ID is presumed.

Documentation and pics reviewed by Ebird, Bird Studies Canada and several published shorebird field guide authors who unanimously agreed this was most likely ID.

Field marks and comments noted :

• bird was clearly equivalent in size to Dunlin
• apparent eyebrow, especially in front of eye is most comparable to breeding White-rumped
• bird appears to be in breeding plumage, and lacks the black breast patch of a Dunlin in this condition. Other photos of this apparent combination show the same missing black patch
• strong streaking of upper breast
• bill is clearly more robust and droopy than would be seen on a White-rumped, although perhaps not as large (difficult to judge) as a Dunlin
• scapular colour appears inconsistent with Dunlin (note I am partially colour blind, so this may be an observation solely on my part due to this condition)
• generally white rump, dark legs etc
• hind toe rules out Western Sandpiper

This bird isn't in winter plumage, as Dunlin are not extensively marked below in winter plumage. The underparts do superficially resemble juvenile plumage, but juveniles molt those feathers quite quickly and the fact that these are fresh and unworn indicates that they are new feathers. Breeding plumaged feathers. The streaking is also much more extensive than even a juvenile Dunlin should show. The scapulars are also new and fresh, but lack the reddish tones of a breeding plumage Dunlin. Instead they have broad buffy edges and dark centers. Again they are superficially to fresh juvenile scapualrs but they edging is much broader and buffier. And they are fresh, whereas juvenile scaps would be incredibly worn by now, and not normally retained this long.

So we have a bird with a superficially resemblance to some aspects of juvenile Dunlin plumage, but with some important differences. The bill is also a touch short, the wings quite long and the body less dumpy than a typical Dunlin. So structurally this bird is off for a typical Dunlin, and it's plumage matches no known plumage of Dunlin.