Ducklings Week 7: Determining gender from wing plumage

It is quite a scandal – our ducks are almost 7 weeks old, and we haven’t even given them official names yet. The nicknames “Baby” and “Quakie” have already got somewhat stuck to their respective owners, but Zorro doesn’t seem to be the right name for our biggest duck, somehow. If he is a drake, his head will eventually turn green and his name won’t make sense any more since you wouldn’t be able to see that thick mask-like eye stripe he still currently wears. If he’s a she, then the name would also still be wrong!  The last two ducks are hard for me to tell apart, and I’ve nicknamed them simply “the Twins”. Neither has distinguished itself in such a way that a name would suggest itself to me; but perhaps I have simply not been paying enough attention to them while nursing our injured Baby duck the last 2 weeks!

Wings03Just a few days ago, while doing research on gender differences in mallard ducks,  I came across a very comprehensive document¹ by a Samuel Carney (of the U.S. Fish and Wildlife Service) that helped me finally determine the sexes of our five mallard ducks. Of course, I could simply wait for the male(s) to moult into their breeding plumage – this would be one of the most obvious indications, but I’d have to wait till they are 4 months of age!

Here is the key sentence (in the chapter on Mallards, page 23 of the document): “Sex Determination: The white bar anterior to the speculum extends onto the greater tertial coverts on all female wings but terminates at the proximal edge of the speculum on nearly all male wings.”

Wings02What the above means in laymen terms is that if you first locate the speculum, or the colourful blue/violet patch on your duck’s stretched-out wing, and then examine the black and white bar bordering it on the top (i.e. the side nearer to the head of the bird), you will see a clear difference in the length of the white bar of the female’s wing vs. that of the male’s. Follow the white bar in the direction of the bird’s body – if it ends at the same place as the black bar, it’s a male. If the white bar extends further than the black bar, it’s a female. The pictures will make it all perfectly clear.

Zorro (Buerzel) has green feathers on his rump!

Zorro (Buerzel) has green feathers on his rump!

So, it’s official – we have one drake, and four mallard hens – who would have thought! Baby is not a he, but a she… and Zorro is indeed a drake. He is at least half again as big as the other ducks, and he is the only one whose rump feathers are turning greenish in hue. We’ve been calling him Bürzel (cute German word for “rump”) because of that, and the name is starting to stick. Oops!


¹”Species, Age and Sex Identification of Ducks Using Wing Plumage“, by Samuel M. Carney, U.S. Fish and Wildlife Service.





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