and birdo as established by nintendo is a girl (and you can't argue with the creators)
OK, let's get things done.
Snails are unisex, therefore Yoshi can be too.
Platypuses give milk to their babies which come from eggs (Just a random fact.)
And there is such a thing called Gay Relationships @Golem
NINTENDO @#$%^$^^#^# ESTABLSIHED THAT HE WAS MALE TOPIC ENDED
Birdo's is debatably transgender, so yes, she would be female. And Yoshi is male. Case closed.
Maddox cox is right, Yoshi is a species, not a character of his own. It can be either gender, or possibly genderless.
Yoshi is a boy. Wait, do male AND female Yoshi's lay eggs? Also, how can yoshis lay eggs so fast? :-|