Sprunghafter Anstieg von Brutstörungen bei Höhlenbrütern

Summary

From 1986 onwards increasing numbers of Great Tits (Parus major) and Blue Tits (Parus caeruleus) were registered “breeding” on empty nests. In 1987 and 1988 up to 4% of all ♀ found sitting on nests did not lay any egg. The rate of breeding failures might be considerably higher because many individuals “breeding” on empty nests could have been overlooked by weekly checks of the nest boxes.