Black Woodpeckers recolonize south-eastern border of their European range

After a range contraction in the south-east of its European range during the twentieth century, Black Woodpecker (Dryocopus martius) is re-colonizing this area since the 1970s. Our analysis of published data revealed average expansion rate 70–180 km per decade, first through well-connected forests along major river systems, and later spreading to isolated forest clusters in East Ukraine. Field studies confirmed that mature Populus stands in riverine and upland broadleaved forests were preferably settled by the recolonizers. A consequence of this recolonization is the re-appearance of large excavated cavities; observations in one territory showed their fast accumulation reaching 10 cavities/km² in 7 years.