Lesser Spotted Eagle Clanga potnarina Brehm, 1831 (Ayes: Accipitridae) in Dadia-Lefkimi-Soufli National Park, Greece: Population Trends and Spatial Use in Respect to Continuous Landscape Changes during the Last 35 Years

摘要

Lesser Spotted Eagle is a medium sized raptor with a stable population within its breeding range. Nonetheless, its favourable habitats (a mosaic of forest and low-vegetation forest-openings, often with water elements such as small ponds and flowing streams), are suffering from land abandonment as a result of abrupt socio-economic changes related to rural depopulation and the decline of traditional agro-silvo-pastoral practices. The species' breeding population in Dadia National Park (Dadia NP) of approximately 20 pairs, is an important stronghold at the southern fringe of its European breeding range. The breeding territories and their spatial distribution trends were studied in Dadia NP for 35 years (1979 to 2012). The overall interannual trend was not statistically significant for the population, with a minimum value of 17 pairs (2001 and 2012) to a maximum of 22 (2005). Despite this long-term stability though, territories' distribution in Dadia NP has changed remarkably. During the 1970s, a more uniform and clearly territorial distribution had been observed in the western part of Dadia NP, the stronghold of the species. It was an area characterized predominantly by forests, mixed with small-extension open landscapes, an optimal foraging and breeding landscape for the species. In contrast, in the 21st Century the population has shifted progressively to the eastern forest lowlands of Dadia NP adjacent to agricultural land, demonstrating a clustered distribution with reduced territory distances in an agro-forest area, not considered optimal for Lesser Spotted Eagle. This noticeable spatial change could be related to a decline in forest openings and habitat mosaics to the western part, as a result of land abandonment. Thus, the most suitable region for the species, decreased from 66% in 1979 to 54% in recent years, and specifically in Zone A of the National Park the most radical change was observed (from 80% to 53%). In conclusion, increased landscape homogeneity and reforestation of open areas could be major threats to the viability of Lesser Spotted Eagle. This has forced the species to shift its breeding territories already towards more humanized areas, in a more clustered distribution and expose them to human induced risks. Conservation policies should strive to increase heterogeneity at the landscape level and decrease the ecological impact of land abandonment.