I have a runt for a U2, and this is his favorite and one of my ekkie's favorite. As the main base I use an ss rod. You can also use a piece of Paulie Rope. But I take two plastic bottle caps, and in between I put either buttons or Rotelle noddles (flat and circular). I don't give much give to the movement of the bottle caps, meaning the bird can't easily lift the top one up from the bottom one. I don't make the movement easy by either tying a tight knot directly above and below the bottlecaps or just cram other stuff on the ss rod. Find a place where you can buy buttons cheap. I bought an assorted bunch of mismatches at Hobby Lobby.
Both Rico and Molly went crazy all day trying to get to the buttons. Perfect toy for them.

That's a great idea Lara- I'll have to try that with Ollie, its about toy making time. She loves to crunch up dry pasta!

Lara - can you post a picture? Sounds like fun! Can you use one of those veggie skewers?

Kathie, a veggie skewer would be perfect! Tomorrow I'm making toys for my kids, I'll make a couple and shoot photos.