There’s a lot to speak of on this matter of Birdo’s gender, hopefully this information can help.
Originally, Birdo was supposed to be officially male, and, wearing a bowtie, was what Nintendo officially described as a confused individual back in the days of
Super Mario Bros. 2 and
Wario's Woods.
But as the Mario sports games (or at least the N64 Tennis game) came around, Birdo was described as female (a trait used in later games such as
SSBM, according to the trophy), and even had a female voice in
Mario Tennis, causing many to joke that the creature was Nintendo’s "first transsexual character". The fact that the official, original, Japanese name of this creature is ‘Catharine’ also points to a female character, but that does not certify it. Then, in
Mario Golf: Toadstool Tour a few years after
Mario Tennis, ‘her’ voice becomes more like that of a Shy Guy’s, and therefore was androgynous (gender-neutral/both male and female). Then I hear that in
Mario Strikers Charged, Birdo is officially referred to as a HE again.
What happened here?
One explanation is that the word Birdo, like Yoshi, refers to both a character and a species. I hear that Birdo in SMB2 appeared in several colors, and each color of this boss attacked differently. I doubt that Birdo was one character that changed colors and battle tactics after each defeat, although such an ability is not exactly ruled out, either.
But then, watch the opening of
Mario Power Tennis (as it can be easily accessed by searching for it on YouTube) and you will see
multiple Birdos of different colors in different scenes. In fact, look at the left side of the first scene, and you’ll see *more than one Birdo along the sideline of the court* as Mario hits the ball. Despite the fact that non-main-story games in the Mario series can be discounted for storylines, it’s still official and very likely to be a depiction of the characters' recreational activities when Mario is not on a quest to save Peach/stop Bowser/what have you.
In the end, I’m assuming that for the appearance of multicolored Birdos in at least TWO games (I know that
Mario Party 7 offers her as a playable character but I can't say whether others aren't seen in the background), Birdo is a species, and both males and females tend to dress alike. The one that is described as female and is said to have a relationship with Yoshi is therefore a different individual than the one(s) that appear in
Mario Bros. 2 and Strikers Charged.
So what gender you see depends on the individual shown in the game…either a male or female may appear at any given differant game.
BUT in terms of what new female characters should appear in Brawl, Birdo could be a playable character, but for some reason I think would be unlikely. It has something to do with what is said about rather minor characters like Shyguys in the first page of that "Negative Nancies" topic stickied on this board. Daisy and especially Toadette would be even more handicapped due to that rule.
Krystal from the new Star Fox games at least has a larger chance of inclusion than Birdo would due to a lot of popularity with this character recently, but we can't say how many SF characters would be included. Fox is in, and Falco could return. I doubt that more than four characters from StarFox would be included as playable, so... if four make it in, Krystal and Wolf O'Donnel are likely to appear. If only three StarFox slots are available, decisions, decisions...what to do, Nintendo, put in a female character, or a villain? Or what if they included both and dropped Falco? Though I'd say that the latter choice seems unlikely.
It could go either way between the first two choices, but I think it would be better to have four SF characters, though it would be a stretch. Five would be too much considering the other franchises. Peppy and Slippy, while important and possible to be unique, would be a bit unfair because why should (what I'm assuming is) four potential slots ALL be covered by the main pilots? I guess they'd be Assist Trophies, which seems respectful enough. BUT if Krystal and/or Wolf were not added and 3 other StarFox slots (besides Fox himself) were open, there's Peppy and Slippy's spots right there, in all likelihood.
As for other female character's chances, I doubt they'll put more than a few. Dark Samus can be counted as a female since the official Metroid Prime 2 scans refer to it as female due to having Samus' (female human) DNA, and she was popular on polls. Doesn't set anything in stone, though.
