Ferruginous Duck x Tufted Duck Aythya nyroca x Anas fuligula
This hybrid seems to be less common than Ferruginous Duck x Pochard hybrids. The appearance of these birds is pretty typical. Although not always obvious the reddish tones to the crown were present on the first bird and also on several other Ferruginous Duck x Tufted Duck hybrids portrayed on the internet. I couldn't make out this feature on the Lowestoft bird though, but there does seem to be a hint of it visible in the photos.
The folloiwing 3 birds from Stiling were on a pond holding just 6 ducks, all of which appeared to be hybrids (the others being 2 Shelduck x Wood Duck hybrids and a Yellow-billed Pintail hybrid). The drake of the trio was obviously a hybrid but the females could have passed as pure Tufted Ducks. After close inspection I concluded that at least one and probably both of these were also Ferruginous Duck x Tufted Duck hybrids - the tuft shape was similar to that of male hybrids, they showed a contrasting reddish tinge to the crown similar to that shown by males, though much less distinct and only visible at certain angles, and at least one bird showed a clear-cut dark-bordered pure white patch on the undertail-coverts.