Crested ducks are basically an aberration appearing in any colour and as such hava mixed history. The crest is essentially a mutation associated with skull deformities and known for hundreds of years. There are those who claim that crested ducks first appeared in Britain, which is unlikely but they were certainly first Shown here and appear in many early poultry books . Genetic mutations appear occasionally all over the world. Selective breeding would then have increased the numbers of birds with the same characteristic. 17th century Dutch paintings show crested ducks on wildfowl such as Melchior d'Hondecoeter (1636 -1695) and Marmaduke Craddock (1660 - 1717) from Somerset in the Uk showed them
The crest is formed from a mass of fatty tissue that emerges through a gap in the cranium.( skull) From this, feathers grow. Crests vary from centrally placed, full crests, rather like powder puffs, to knobbly protuberances with just a few feathers; or the occasional earring when it has 'slipped'. The crested gene can be bred into any breed except Muscovy as one parent crested will breed a percentage of crested offspring .All crested seldom breed successfully but if they do produce better stock. If using a crested female with a large crest watch as the drake uses this as to ' assist ' mating and she can get injured easily. The tuft of feathers on the head, which occasionally appears, having been recognized as a point of attraction, selected and bred for of the off spring many will be plain headed but carry the crested gene so a crested drake will turn any breed crested . . they also have the energy for this so watch out
The crest gene is an incompletely dominant one. ie, if an chick receives a double dose of the gene &endash; one from each parent (homozygous) it will die in the shell. If only one of the parents passes it on (heterozygous) the resulting hatches will be :- 25% will not hatch, 25% will not have crests and 50% will have crests. If a crested heterozygous bird is crossed with an un-crested one, the resulting hatch should be 50% crested and 50% plain. So, as you can see, breeding Crested ducks is challenging and not recommended for beginners; also if the crest is so large as to intefere with normal eating and mating etc it would need to be 'trimmed' to allow the duck a normal life.
The domestic Crested Duck is a duck breed descended from the Mallard. It has its appearance because it is heterozygous for a genetic mutation causing a deformity of the skull. As a result, when a pair of crested ducks breed, the young sort out in the usual 1-2-1 ratio:-
If a crested duck and a non-crested duck breed together, the resulting ducklings would be expected to be 50% crested and 50% non-crested.
If you breed two crested together expect some of them to not hatch because of the crest not being fully devoloped.