I created this macrame pet climber or ladder with hermit crabs in mind, but I think birds would like it very well too.  I made it with bamboo skewers, 100% sisal twine and acrylic (plastic) beads.  It was very difficult to make and my hands are raw from the rough sisel fiber, but I love the results.  I may try to make a crochet version, which would make them easier to construct.