well I've had no luck with the partridge eyeliner trick. I usually get more with eyeliner than no eyeliner and both male/female will have it. Wish it worked for me!I wrote : "Depends on the coloration, Partridges you can tell from day 1 !"
This is reliable on "pure" Partridges = eb/eb* (Silver & gold) it is'nt reliable on wheatons = eWh/eWh or eWh/eb.
* "pure" Partridges can't have other mutations as Co, Db, cha, B, choc, lav