Choice of nest boxes by Tree Swallows, Tachycineta bicolor, House Wrens, Troglodytes aedon, Eastern Bluebirds, Sialia stalls, and European Starlings, Sturnus vulgaris

Controlled experiments with nest boxes mounted in sets of two or three in which one feature was varied were done from 1975 to 1983.Tree Swallows preferred boxes facing south, a floor plan of 15.3 x 15.3 cm to one 10 x 10 cm, and a depth from the bottom of the entrances to the floor of 12 cm to 16.5 cm.House Wrens preferred entrances 3.2 cm in diameter to ones 2.2 and 2.5 cm, but readily used holes 3.5 and 4.4 cm.They preferred a floor plan 10 x 10 cm to one 15.3 x 15.3 cm.They rejected white but accepted black interiors in long low boxes, but accepted both black and white interiors in upright boxes which admitted less light.Eastern Bluebirds preferred entrances 4.4 cm in diameter to those 3.5 cm.Three times as many Eastern Bluebirds used boxes with a floor plan 10 x 10 cmas used those with a floor plan 15.3 x 15.3 cm.European Starlings (Sturnus vulgaris) preferred goldeneye boxes 33 cm deep to those 24 and 18 cm.Competition among species might be reduced by using features preferred by one and disliked by others.