Two experiments tested the preferences by tits in pinewoods for different nest box designs. Great, Blue and Coal Tits preferred deep boxes (≈ 19 cm from base to entrance lip) over shallow ones (≈ 9 cm). Crested `Tits preferred boxes that had been filled with sawdust and wood-shaving which they removed before nesting. The excavation of a fresh nest cavity each year perhaps ensures that nests are free of fleas for Crested Tits.