They are all female.
Earlier in the year (spring and early summer), the ducks had paired off, with some females unattached to male ducks. Babies were born, and the male ducks were still hanging around.
But those male ducks were asshats. They constantly harassed the female ducks, driving them away from their babies (who would then cry for mama and attach to another mama just so they weren't alone). As the summer progressed, the female ducks started hanging around together more often, even protecting each other from the male ducks.
Now there's a flock of all female ducks in our apartment complex, and I haven't seen a male duck in months.
We've dubbed them the Amazonian duck flock because they've banded together to be strong against the onslaught of harassment. They watch out for each other, and I rarely see any of them separated from the group.
They're my favorite ducks ever.
* By which I mean they live on the property outside, not that they inhabit units. Just to clarify.