"Désolée d'être si fatiguée" Why feminine?

I came across this example explaining “désolé”, is “désolée” and “fatiguée” feminine only when the speaker is female? Thank you!

Yes. If a man was speaking, then the masculine would be, désolé d'être si fatigué. 

A woman would use the feminine version and a man the masculine.

masc: I'm ready now - je suis prêt maintenant

fem: I'm ready now - je suis prête maintenant

@tenletters, Thank you for your reply! That solves it.