Wry tail is when a chickens or ducks(not sure on all types of poulty/fowl it affects) tail is leaning to one side, it can be a slight turn or it can be drastic. It does not really affect their health in anyway, but you do not want to breed them since the gene for it is double recessive. So that means it will get passed down no matter what, either 100% or 50%.

(ww) bred with a double dominant (WW) alleled chicken, you produce more chickens (100%) with a hidden non-expressed recessive allele for wry tail (Ww).

ww=wry tailed
Ww=normal tail with wry hidden recessive
WW=normal tail, no recessive

then mating her with a WW produces 100% Ww

mating her with a Ww produces 50% Ww and 50% ww

mating her with a ww produces... obviously 100% ww