The black woodpecker Dryocopus martius has a large Eurasian range, occurring in temperate and boreal forests, and is categorized as Least Concern on the IUCN Red List. Along the southern fringes of its range, populations tend to be fragmented and rely on remnant mature forest patches, usually in highlands. This was the situation in Spain in the 1980s and 1990s, when the species was only known from two small populations, separated by 150 km: the Pyrenean and the Cantabrian.

But in the 2010s, monitoring revealed an unexpected range expansion. The black woodpecker was recorded breeding far from its former known range, leading to coalescence of the Pyrenean and Cantabrian sub-ranges. Previously considered a typical mountain and remote forest dweller, the species has colonized lowland, secondary forests and commercial plantations, and can even be found at sea level. This expansion is ongoing, with news of the species’ establishment in Central-Mediterranean Spain, c. 250 km south of the previously known range. Surveys in February–June of 2021 and 2022 in this area have inventoried occupied territories and breeding cavities.

The biological or demographic causes are unknown, but the species’ range expansion was simultaneous with the maturation and encroachment of forests as a result of a reduction in forestry and livestock activities. Functional connectivity models match the observed distribution pattern, suggesting that colonization events were influenced by landscape spatial structure and the performance of long-distance dispersing individuals (Gil-Tena et al., 2013, European Journal of Forest Research, 132, 181–194).

In this expansion, the species has begun to occupy commercial plantations of Pinus radiata, an introduced North American conifer. This pine was extensively planted during the 20th century in the Spanish Basque region, and comprises 30% of the forest in this area. Pinus radiata plantations are intensively managed, and timber is harvested in 20–30 year cycles. It is unclear whether this habitat provides good quality resources for the black woodpecker, or is a sink, with woodpecker numbers sustained by immigration. Demographic parameters support the latter hypothesis, but the evidence is inconclusive. Research on how species tolerance can buffer pressures in human-made habitats has practical implications for adaptive conservation and for the compliance of commercial forestry practices with biodiversity requirements.