Chestnut Flanked White Zebra Finch Gender?

I just got a new chestnut flanked white (CFW) zebra finch in hopes to breed. It looks exactly like a female CFW, with an orange beak and a brown teardrop beneath the eyes, but it sings. Not as much as my male zebra finch, but still makes quite loud, rather high-pitched calls. Is it usual for female zebra finches to make calls, or is my "female" really just a male?