It doesn't work on all Lutinos, I have one that you can't see any bars or dots on her and every method to find them was used bright lights, flashlights etc.... she has no markings on her that are visual to the eye.You can visually tell on lutinos. It is harder to see but the females will have the bars on the under side of the tail and spots under the wings. It will be yellow on white. I have a lutino female. I used a small flash light to see better. I am a breeder and I found out how to sex birds on all that can be sexed by looking. A DNA test is a sure way to tell but if it has the bars and spots its a girl.