Actually, there are quite a few males there, Chris--but the young-of-the-year all look like females. This time of year, the adults are all migrating, leaving the local nectar sources to their young.
Some young males have light barring on the throat, like in the first pic on post #8. But I usually look at the length of the bill. If you reversed the bill and poked it through the head (
) if it would poke out the backside of the head, the bird is probably female. A bill that is shorter in proportion would indicate a male. I have no way of proving this is true in the young-of-the-year, but it's a reliable way of telling a male from a female adult (and easily checkable because of the obvious differences in adult birds
). So even in near dark, with the birds in silhouette, you can tell males from females.