Strange bugs on gold finch sock feeder?

I've always hung a sock feeder for the finches, even when I lived in an apartment, I hung one in the tree outside my window. I finally bought my first home last year and hung a sock feeder in the dogwood tree outside. Within a day or two, the goldfinch started showing up to feed and continued feeding for about 2 weeks. Then they suddenly stopped using my feeder :( When I removed the sock feeder I noticed what looked like tiny/baby red ants all over it! This must be the reason the birds stopped feeding on it. I've never seen this before...ever! I was raised using the sock feeders and I have always had one, except now. I'd like to put one out again, but what happened? How do I prevent these tiny red ants (I'm thinking that is what they are, but not sure) and why were they all over the feeder? Any suggestions? Thank you! I miss my finches :(