No wonder the hummingbirds were staying away from the feeder! I went out into the garden to see why they were ignoring all that nectar, and why the level wasn't going down. I still don't know the answers to those questions, unless hummingbirds hate ants as much as I do.
Not only were ants crawling all over the feeder, but there was a line of them all along under the eaves and up and down the cord that the feeder was hanging from. Eck! I can live with spiders (not that I have any choice) but when I see ants anywhere near the house, I go a little nutty.
I ran back into the house and got my stepstool and a can of unscented Raid. Then I sprayed massively, until I couldn't see any more movement. I pulled the feeder down, emptied it, washed it out thoroughly and stowed it in the garage until I could decide what to do next.
The hummers are perfectly happy, for the moment, with all the various blooms throughout the garden, and there will be more plants coming to life now that spring is finally here.
The fumes must have got to me, because I had to sit for awhile with my eyes closed until the light-headedness went away. I guess I should have been wearing a gas mask, but I understand those are in short supply these days. After I got my senses back (shut up), I went back out and flushed the area with water, to try to minimize any collateral damage.