Oyvind Saeteren’s scientific contributions

To assess whether modern forestry practices pose a threat to the black woodpecker (Dryocopus martius), we studied nest-site selection and reproductive success in an intensively managed, boreal forest landscape of southcentral Scandinavia during 1990-95. We recorded 501 nesting events in 457 excavated holes in 367 trees, of which 180 events were monitored for reproductive success. Radiotelemetry was used to monitor 219 birds. All naturally occurring tree species were used as nest sites, but most nest holes were in live aspen (Populus tremula; 50%) and Scots pine (Pinus sylvestris; 25%). Dead trees were rare (8% of available nest-trees, 0.7 dead trees/100 ha) but constituted the most strongly selected tree type, being used 2.5 times more often than expected from random use of nest trees. The birds selected trees retained on recent clearcuts (used 2 times more often than expected), and they avoided trees in old forest. Selection of nest habitat was consistent with nesting success; the predation rate was lower and fledging rate was higher in clearcuts than in old forest. Selection of nest trees was not consistent with nesting success; the predation rate did not differ, but fledging rate was lower in dead trees compared to live aspen and pine. Habitat characteristics of cavities used for roosting (n = 124) did not differ from cavities used for nesting. Aspen and pine reached minimum critical dimensions (36 and 40 cm dbh) at the age of 55 and 110 years, respectively. In boreal Scandinavia black woodpecker nest sites do not seem to be threatened by modern forestry, provided that dead and green trees are retained on clearcuts and that scattered aspen trees are allowed in young conifer plantations.