Appl. Entomol. Zool. 40 (4): 575–577 (2005)

The nest box is a powerful research tool for ecological and conservational studies of birds and several other cavity nesters. However, skilful predators such as martens sometimes invade nest boxes, thus disturbing researches. To protect nest boxes against predation by martens, we attached a small plate inside the nest box below the entrance hole, and we report here on the advantage of this device. In 1999 and 2000, respectively, 73.0% and 64.8% nest boxes were used by the Great Tit and the Varied Tit. After fitting boxes with the plate in 2000, the percentage of predated nests by martens decreased from 22.4% to 5.9%, and the percentage of successful nests increased from 29.3% to 43.8%.