The Stanwick ‘Ferruginous’ Duck

It’s not called ‘Fudge Duck’ for nothing. Closely resembling the real thing, hybrids abound, enticing observers into a ticking temptation trap, in which nothing is quite what it seems …

When the news broke of Ferruginous Duck or hybrid at Stanwick GP, at around midday yesterday, it was clearly a sensible move to throw in that cautionary caveat – the dreaded ‘h’ word – as rare ducks are notorious for carrying rogue genes. Although looking good at first sight, this was one such bird which, upon closer scrutiny, clearly did not pass muster. OK, it could be said it was mainly but unfortunately, not wholly, Ferruginous. The following assessment is based upon published images of the bird and follows the most up-to-date ‘hybrid checklist’ of features given by Reeber (2015).

It is assumed the bird is an adult female on account of the iris being dark brown (paler in juvenile/first-winter). In terms of size, it’s too large for a Ferruginous Duck. Two of the images below suggest it is virtually the same size as a Pochard. It also appears too bulky. Ferruginous Duck is small and any bird close in size to, or larger than, Tufted Duck is likely to be a hybrid.

Female Ferruginous Duck-type hybrid, Stanwick GP, 25th January 2020 (Adrian Borley)

Female Ferruginous Duck-type hybrid, Stanwick GP, 25th January 2020 (Adrian Borley)

Head shape is not perfect for Ferruginous Duck and is similar to Pochard. On close inspection, the head shows two slightly paler brown patches, one at the bill base and one on the rear cheeks, which is strongly indicative of hybridisation with Common Pochard. The bill colouration also indicates a hybrid as the pale subterminal mark extends along the sides of the bill, which would form a ‘U’ shape when seen from above. The subterminal mark should not extend in this way (although many published images of so-called ‘pure’ Ferruginous Ducks show it – including some of Reeber’s – so its validity may be questionable). There also appears to be fine traces of black at the bill base – another hybrid characteristic.

Female Ferruginous Duck-type hybrid, Stanwick GP, 25th January 2020 (Steve Fisher)

Female Ferruginous Duck-type hybrid, Stanwick GP, 25th January 2020 (Steve Fisher)

Female Ferruginous Duck-type hybrid, Stanwick GP, 25th January 2020 (Adrian Borley)

The belly is not sharply demarcated as it should be for an adult and it appears a little smudgy. Also, there appears to be a slight demarcation between the breast and the flanks, which is not right for Ferruginous Duck.

Female Ferruginous Duck-type hybrid, Stanwick GP, 25th January 2020 (Steve Fisher)

All the above features exhibited by this bird indicate a hybrid origin. Reeber suggests that hybrids are relatively frequent in the wild and even goes as far as stating that in Western Europe, hybrid-like Ferruginous Ducks are commoner than pure individuals!

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