We focused upon habitat use and home range size variation in an alpine population of the Black Woodpecker Dryocopus martius. Habitat selection analyses showed that the dominant local forest type, i.e. Mountain Pine Pinus mugo uncinata, was significantly avoided. Scots Pine Pinus sylvestris stands were positively selected, likely because of the abundance of ants; Beech Fagus sylvatica was chosen for nesting and roosting. A high level of flexibility in ranging behaviour and habitat selection, with remarkable among- and within-individual variability, was recorded. We assessed the reliability of census techniques by comparing results obtained by radio-telemetry and territory mapping, which showed that territory mapping failed to identify all pairs detected through radio-tracking. Several behavioural and ecological traits may bias count results irrespective of the methods used. Mapping methods are particularly ineffective because the Black Woodpecker is weakly territorial: in our study area home range overlap was rather high and no territorial defence was detected. Based on these results, the potential of the Black Woodpecker as ecological indicator is questioned.