Ring-necked or Tufted Duck?

 Partial view of the Laguna de Barlovento

First of all, my apologies for the exceptionally poor quality of the photos in the present post. To give an idea of the observing conditions, above is an uncropped, partial view of the Laguna de Barlovento reservoir. There are at least 5 birds in the photograph: fairly conspicuous in the lower centre is a Coot (Fulica atra); to the right of it are 3 very indistinct Common Teal (Anas crecca); and in the centre of the image, up against a clump of vegetation, is a solitary black and white duck. It is the latter bird which enticed me up to the far northeast corner of the island on what turned out to be a miserable, windy day...

As mentioned in the previous post, in January this year a male Ring-necked Duck (Aythya collaris) was reported by a visiting birder at the Laguna de Barlovento. This is a difficult location without a telescope, as the entire reservoir is fenced off, and it is impossible to get close enough to its banks for good views of the water with binoculars. An added incovenience is that weather conditions are often less than ideal, with poor light and blustery winds being frequent.

The reservoir is presently full to about 30% of its capacity, according to an estimate in the local press. This implies height differences of at least 20-30 metres between all accessible vantage points and the water surface. The resulting downward angles of vision may account for the fact that, in these photos, the drake's head does not look as characteristically large and pointed as might be expected for Aythya collaris. Perhaps the following view from the rear gives a better idea of its true shape...

Moreover, several other identifiction features visible in these photos indicate the Ring-necked (A. collaris) rather than the Tufted (A. fuligula) Duck: absence of tuft, white subterminal band on bill and white band at its base, flanks grey in colour with white vertical  "spur" at front, upper edge of flank panel more markedly S-shaped than on Tufted, longer tail...

After close examination of all the photos I managed to obtain yesterday, my opinion is that this is the male Ring-necked Duck, correctly identified and reported to the Spanish Rarities Committee by another observer in January this year. Opinions and comments would be greatly appreciated.