Woah! How could I miss this question? :blink: Sorry to keep you waiting.
I knew the problem with their wings will come up sooner or later... :unsure:
Well, male wingtail wings are completely feathered. No membranes at all.
Female have membraned wings, but with a secondary pattern of feathers attached.
Now I'm not a scientific guy, I just gave them different wings to differ who's male or female. I was young and thought the idea was cool (though, the way I draw female wings doesn't look as good as male wings).

Aah... things like this regarding character designs makes me feel sad and unsafe about their current appearance.
I would like to see them more realistic, but I have no idea how.