possible Laysan Duck x Yellow-billed Pintail, River House Restaurant, Stirling (Stirlingshire, UK), 29th December 2013 - copyright Dave Appleton
(photo ID: 0382)
This is another one where the ID is far from certain. Another possibility, thanks to Joern, is Laysan Duck x Yellow-billed Teal (Speckled Teal). The leg colour, plumage markings and hint of slightly upturned central tail feathers are suggestive of one of the Mallard group (which includes Laysan Duck) and the small size and hint of a pale eye-ring are what made me think of Laysan Duck. That's by no means certain, which makes working out the second species even harder!
There were only six ducks on the pond and all of them were hybrids. I don't know how they got there - perhaps they're owned by the restaurant adjacent to the pond (but then why only hybrids?), or perhaps they were released there by a wildfowl keeper who doesn't like hybrids?
possible Laysan Duck x Yellow-billed Pintail (same as in photo ID 0382 above), River House Restaurant, Stirling (Stirlingshire, UK), 29th December 2013 - copyright Dave Appleton
(photo IDs: 0378-0381)
Laysan Duck Anas laysanensis
Yellow-billed Pintail Anas georgica
Yellow-billed Teal Anas flavirostis