Table 1 Laying dates in April date (1 = 1 April, 31 = 1 May) and number of breeding pairs (in parentheses) of common nest box breeders in all our study plots (1050 nest boxes) in Dwingelderveld, Drents-Friese Wold, and Boswachterij Ruinen [30]. Mean April temperatures are in degrees Centigrade