Is Yoshi a boy or a girl

Some say Yoshi does not have a gender, though the "female" Birdo has a crush on him or her. But, Birdo has been proven to be male in many ways.
Nintendo says that.

Here is the explanation:
The characteristics of a male Yoshi are:
for behavior more aggressive,
for appearance, There is barely any differences from the female but the do have more spikes. sometimes, they can go all the way down his back.
The most apparent characteristic that differs from a female Yoshi is that he can't lay eggs. However, there are a lot of males seen in games despite this fact. That's all really. Sometimes, males would lose their spikes from combat, making them easier to ride.

The characteristics of a female Yoshi:
Less spikes, ability to lay eggs, calmer too.
She has a motherly mind, meaning, when she finds a lost baby or creature, she will take care if it until the parents are found. If you played Yoshi's island, That is a great example of what was explained above. Not make males look bad though but, they would attack baby Mario for coming into his territory or space.
It is unknown how the female Yoshi egg became so popular but probably she uses it to defend herself from predators that may hurt her or her baby. That explains why the female Yoshi throws eggs. Yes, she lays eggs. No, she doesn't wear a bow or have big eye lashes.

So now you know the difference between a male and female Yoshi.
Yoshi is most likely a girl. But yoshi, the species, can be boy or girl.