Tailless Cuckoo Marans

[JuliB]

One of my cockerels I am growing out has a “non standard” tail. It’s not completely absent like an Araucana, but it’s definitely small and rounded, more like a Cochin tail.
Does anyone know of the genetics at play here? Obviously he can’t stay in my breeding pen, but wondering what i would get if I used him in my Olive Eggers.

 

[JuliB]

he was more cooperative about pictures this morning

 

[Amer]

Probably not genetic at all. While genetics are sometimes the cause, random rumpless birds will pop up in any breed.
It is caused by an hatching deformity but it does not affect the health of the bird. It isn’t genetic.