It turns out it wasn't food I should have been concerned about. It was snow. I returned today to see two of the three homemade feeders missing. A huge slab of snow slid off the roof, and took the feeders with them. I knew snow slid off the roof right there, I just didn't realize they were directly in the slid-off path. So two of my feeders are burried under about 4 or 5 feet of snow. I just hope there were no birds on the feeders when it slid.
The snow slab from inside looking out. The hole I dug trying to find one of the feeders is on the right.
I tried to dig one of the feeders out, but after excavating a hole as deep and as big around as I am tall, I still hadn't found it. Sigh. All I could do was re-fill the one remaining feeder, throw some seed on the snow, and call it good. And I was actually rewarded with a short visit from a new feeder friend - a single White-crowned Sparrow.