The Pacific Diver at Marazion, 2 Nov 2009

As I was unable to take pictures of this elusive bird, I first postbhere my notes and a short description of my observation, leading to the conclusion that the bird was indeed an adult summer-plumage Pacific Diver. First detected near rocks at 9:00am, and seen during maybe 20 seconds, the bird was actively (frenetically) diving, and despite intensive search at the same site, it was only relocated, at excatly the same place, 3 hours later, when it was seen twice ten seconds between dives, then about 30 seconds in a raw as it was preening. During this last observation, the bird underparts were distinctly observed. Leaving the scope to take a camera, the bird disappeared again from view and could not be relocated later. On the contrary, the adjacent Great Norhtern Divers (7 birds at least in the bay)à were easy to see and relocate.

The bird was clearly an adult in summer plumage, and below are reported the notable differences with the 'local' black-throated divers.
First seen criteria was the blackish foreneck, throat and face (including eyes) and contrasting with the pale nape and upper hindneck. Concerning the jizz and shape, the head appeared very rounded, giving the bird what I called a 'teddy bear' expression' (slightly disproportionate large and rounded head). No white at all along black flanks, below the wings as well as on rump sides. Absolutely no white patch on sides of rump: this was the case on the swimming bird as well as when the bird was preening. During the last observation, the bird was preening its belly, turning its body on the water, which made the underparts and undertail coverst visible, so that I noticed the presence of a black line joining the leg bases across the vent. This line was continuous and large, as large as the tarsus. All these criteria seem to confirm that this bird was indeed an adult Pacific Diver, as a Black-throated would have had at least a white patch on the rear flanks (even in breeding plumage, if not a white line along flanks), a less contrasting nape and a paler area near eyes, and at most an indistinct incomplete black line between legs. Apparently, this bird (or another) is reported each winter at this site, since its first discovery at the end of the winter 2006-7, then in winter plumage.