One of the CZTs I read about used "feathers" as a ZIA (Zentangle Inspired Art) for her Part II class. This feather is about 12" x 4". I think her's were much smaller. It is done on the smooth side of tinted pastel paper. Those she posted had just one tangle across the width (rather than two different ones). So just 6 instead of 12.
This makes sense in class as this feather took quite a bit of time to draw. She had them trace a pattern for the feather to start with.
Might be a fun activity for my next class.