Always difficult to say for certain if a particular owl is a female or juvenile as markings are much the same. Even juvenile males can have the black/brown barring…until they begin to mature and become all but pure white.
Females have thicker, darker barring on the tail feathers (4-6 bars)…most visible when seeing the South end of a North bound owl.
As a general rule I go by mass/size…females being larger than males. Which at times can be difficult to determine…if I’m wrong then so be it.
Never the less it’s always great to see the Great White Owls from the North during the winter months.