I use cedar for my purple martin boxes, and also might add cedar shavings to try to reduce insect parasites; I'm not aware of any problems. The late Jack Davis recommended the addition of the cedar shavings, and he certainly did well with his colonies in the south sound. I've participated in nest box prep at major martin colonies such as Woodard Bay, and we always have added fresh cedar shavings after cleaning out the old material. I wouldn't say that the cedar is essential, but it's certainly not a problem in my opinion. In the past couple of weeks I've put up about 20 cedar purple martin boxes.

Kevin Li
Ballard, USA
kdli at msn.com