Background:
The Iberian Peninsula represents the southwestern boundary of Middle Spotted Woodpecker´s (Dendrocopos medius) distribution range, where this species shows a discontinuous distribution with potentially isolated populations (see Fig.1A & 1B; [1, 2]). It is currently well-known that one of its main Iberian populations is located in Izki Natural Park (Araba), but this important Middle Spotted Woodpecker population was not discovered until 1993 [2, 3].
After its unexpected discovery, the first censuses specifically devoted to establish the status of the Middle Spotted Woodpecker in Araba province were carried out in 1994 and 1995 [3, 4]. These surveys and unstandardized observations in later years revealed that the distribution of this species was primarily confined to Izki forest and its immediate surroundings in the southeastern part of the province (see yellow area in Fig. 1C). As a consequence, most subsequent research efforts on this species have been mainly focused in this core area [5].
In the last decade, however, several sightings suggested a breeding range expansion of the species from Izki to other nearby areas (e.g. Vitoria Mountains), where Middle Spotted Woodpeckers had not been detected before [6]. This fact was confirmed in 2010 during a study aimed at establishing its status, potential distribution and population density in the municipality of Vitoria-Gasteiz (see blue area in Fig. 1C; [7]). Additional observations, particularly in 2012 and 2013, further revealed the existence of Middle Spotted Woodpeckers in other distant areas (see question marks in Fig. 1C), such as some woodlands of the eastern part of Araba Plain and the southern slope of Elgea-Urkilla mountains, whence this species seemed to have disappeared two decades ago [3, 4].
Conclusions:
The current distribution range of the Middle Spotted Woodpecker in Araba is not clear after nearly two decades since the first regional census.
Several observations suggest that, similarly to other conespecific populations [8, 9, 10] and other forest-dwelling species (e.g. Black Woodpecker Dryocopus martius; [11]), Middle Spotted Woodpeckers might be undergoing an increasing expansive process in Araba.
A new comprehensive study in the province would be helpful to clarify its current status, which is particularly relevant given that the Middle Spotted Woodpeckers present in Araba constitute the main contingent of one Iberian peripheral population that might be locally adapted to supra-Mediterranean environmental conditions, a circumstance that would have important ecological, evolutionary and conservation implications [12].
Acknowledgements:
We want to thank José María Fernández, Josean Gainzarain, Alejandro Onrubia, Fran Silvan, José Manuel Vadillo and Javier Villasante for sharing their field observations, and Tomás Crespo for providing the wonderful picture of the poster.
Azaitz Unanue, Mikel Salvador, Iván de la Hera & Galder Auzmendi
Grupo de Anillamiento Científico de Aves Txepetxa, c/ Vicente Aleixandre 10, 2ºC, E-01003 Vitoria-Gasteiz, Spain.
(Contact email: txepetxa@txepetxa.org)
