WELL...... I thought we don't have to argue for it
since species of dinasours are all transexual in this story
whatever, Birdo can be female if she wants, not vialting natural discipline
though in early details of SuperMarioUSA, Birdo was truly a feminine male dinasour
for the character Birdo, despite her transexual nature
she may want to share some interests and tastes like human being or other species who can enjoy girl things
but it didn't mention the aspect of love, especially her uncertain relationship with Yoshi......
what if dinasours have a crush and want to build a family?
maybe two spouses give birth to each one own child ? :P