There are a number of characteristics which the fancier considers as defects or deformities and which probably have a genetic basis. Such traits as wry tail, split tail, squirrel tail, drooping tail, split crest, split wing, slipped wing, and twisted feathers would fall into this category. The inherited bases of these conditions have not been reported, but most if not all are possibly recessively inherited. Somes (unpublished) made crosses between wry-tailed and normal tailed birds and all F1 progeny were normal-tailed.
Tail carriage varies considerably among chicken breeds and thus is an inherited trait with probably more than one locus being involved. Poultry breeding and genetics By R. D. Crawford