Beavers (Castor fiber), as typical ecosystem engineers, alter living conditions especially for amphibians through the building of dams and felling o f trees, thereby changing the hydroperiod and substantially affecting forest succession stages. In this study we quantify the effects of beavers on the availability o f am phibian breeding waters in the Hiirtgenwald, a woodland area in the Central European Rhenish Massif, its colonisation by com m on frogs (Rana temporaria) and the effects o f age and succession stage o f beaver ponds on ovipositional site selection. In 2013, beaver ponds comprised about half (49%) of all lentic water bodies but contained 82.5% of all com m on frog egg masses. M ature beaver ponds (> 6 years old) harboured approxim ately h alf o f the egg m asses (n = 775), but new beaver ponds (1-3 years old) can also be hom e to large breeding aggregations. Abandoned beaver ponds are o f m inor im portance as ovipositional sites for com m on frogs. High egg masscounts were also found in artificially-dammed ponds (n = 216). We believe that com m on frogs prefer occupied beaver ponds as ovipositional sites because o f high insolation and a perm anent hydroperiod, which lead to rapid tadpole emergence. Beaver ponds are generally located in close proximity to each other, facilitating m ovement and rapid colonisation by com m on frogs. O ur research provides additional evidence to show that beavers enhance habitat availability, heterogeneity and connectivity, thereby fostering am phibian populations at a landscape level. As natural elem ents o f small streams, beaver ponds must be taken into account in the context of the EU Water Fram ework Directive.