- 150 pairs of Schwegler∆ žwoodcreteÓ bluebird boxes were erected near Davidson, NC. Paired boxes were pole-mounted 1 m apart.
- Box pairs were assigned to one of two treatments. In the žsame heightÓ treatment, both boxes within each pair were erected 1.75 m off the ground. In the žhigh-lowÓ treatment, one box in each pair was erected 1.5 m off the ground. For all treatments, initial nest site choices were recorded.
- In the žsame heightÓ treatment, successful boxes were randomly assigned to two treatments: control (old nest left in) and experimental (old nest removed). Subsequent nesting choices were then recorded.
- In the žhigh-lowÓ treatment, all successful first nests were left in. Subsequent nesting choices were then recorded.