I've been delaying beginning my "winter bird feeding" until I was pretty sure that the natural world was not supplying enough of what they need. Of course I don't really know when that is, but when the birds started to check the empty feeders more vigorously I thought that it may be time.
Ditto for these, just plain old brown sparrows, I think. There seem to be scores of them around and they aren't too nervous, as they let me get close to them---which I certainly can't say for both the male and female cardinals, woodpeckers and others that appear at our feeders only in the winter.
I have this window feeder in my room, one on a pole outside below my windows, and one right outside the inner courtyard doors. Keeping them all in food and with a little water in the nearby bird bath, takes some real dedication, especilly when the snow piles up. But, the sisters (and I) love to see them throughout the winter months, so it's certainly worth it.