Duck or Drake? - How to Tell the Sex
Telling the sex in adult ducks is obvious - ducks give a loud quack and drakes make the quieter Donald ‘Duck’ scraping noise. This voice-change from the duckling’s peep into adult mode happens from 5 weeks of age. Listen to birds carefully. Pick them up individually to make sure of their noise.
Young birds develop juvenile ‘duck feathers’ between 4 - 8 weeks. These first feathers superficially resemble the adult female. It’s the subsequent moult into adult feathers (nuptial plumage) between 10 - 16 weeks that makes the big difference. Drakes then develop the sex-curl feathers on the rump.
The adult wild Mallard male sports a green head, white collar and claret bib, and some of the domesticated ducks such as the wild-colour Rouen and Mallard Runner follow this pattern. This basic colour and pattern has been complicated by mutations selected under domestication.
However, other than white birds, drakes have a characteristic ‘hood’ of glossy green, blue or brown, depending on the variety e.g. Cumberland Blue male Runners have a distinct hood.
Another key area is the rump, where coloured males are often darker. Fawn and Trout Runner drakes, even at 5 - 6 weeks, show a darker rump than the females which have a lighter ground colour.
Coloured feathers aren’t 100% reliable to the unpractised eye: they change over the season. Adult males go into ‘eclipse’ camouflage plumage in summer, and look very like the ducks.
Beaks, Legs and Feet
Bill colour is a good guide to the sex. In many breeds/colours drakes have green bills, and females have orange, brown-orange or dark bills. This applies to Rouens, Appleyards, Welsh Harlequins, and to Trout and Silver in Runners. Of course, white breeds show no difference at first: the bill is often orange-yellow in both sexes, but the beaks of adult females often develop darker markings with age.
A word of caution: some females can have dark greenish bills e.g. Abacot Ranger, but their counterpart males are brighter green. And in dark-billed types such as the Fawn and Black Runner, all bills are dark to start with.
Commercial chicks, ducklings and goslings are vent-sexed by an expert, unless they are from reliable strains of auto-sexing breeds where fluff colour denotes the difference. Vent-sexing is practised on Campbells and commercial whites.
Caution: if your Runner ducklings are from ‘mixed up’ colours, they may follow no particular colour-rules for sexing.