00boo, he's right. Birdo is the new name of the enemy that spits eggs from his (or her) mouth in Super Mario Bros. 2. Ostro was the original name of the enemy.
Birdo is a girl because in Super Mario Advance, she has a female voice.
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"Bwa ha ha! Guess who it is, loyal Mario fans...
It is I, King Bowser... ruler of all Koopas, big and small. I have come to take over the Mushroom Kingdom (no, not the place...I mean the WEB SITE!)! Deezer, you will surrender your troops to me, or else you will never see your precious Mario again! Bwa ha ha ha ha ha ha ha ha ha!"