i tot the turtle is the only "female" in their world. i think i read it somewhere in his arc
I think it would make sense for kureha to be female as well because he has very strong maternal instincts, he mentioned to Nagi how he wanted to raise a chick of his own, and the human summoned for him (which is based off of his own tastes and desires) was a neglected child for him to take care of, I believe that if they didn't need to have sex for him to become a divine beast, they would be just like father/mother and son...
The turtle is female towards the black dragon Nagi. More like the black tortoise has a male and female part, with the male being Nagi the black dragon, and the female being the other part of the black turtle, whose name I don't remember.
is birdie the bottom??????