Migratory birds are equipped with a sublime navigating and aviating machinery, which allows them to travel impressive distances with meticulous precision between breeding and non-breeding (wintering) areas twice every year. In order to complete their risky journey successfully, they are highly dependent on qualitative (suitable) and well-connected stopover and staging sites, where they can rest and refuel. Despite the phenotypic and evolutionary plasticity of migration, especially migratory bird species are showing widespread and severe declines. These decreases are attributed to habitat deterioration and human disturbance.Reflecting the integrity of entire flyways migratory species are sentinels of their environment. In addition, they enhance ecosystem resilience by connecting communities at large spatial scales. Given these facts, filling the gap of knowledge about the status (habitat availability) of travel routes between breeding and wintering quarters is stringent. Even more because climate change will significantly alter the pivotal areas that Palearctic-Afrotropical migrants depend on, such as the Mediterranean region, which provides several bridgeheads to cross the Mediterranean Sea (an important barrier), and the Sahel, the last/first major refueling option before/after crossing the Sahara desert (another major barrier for trans-Saharan migrants).For a spring migration situation we quantitatively investigate the habitat availability (i.e. habitat suitability and connectivity) by combining information from four different but nested geographical extents1 centered around western Greece (including the Ionian Islands) and northern Cyrenaica (Libya), for seven common trans-Saharan migratory bird species2, which represent an ecological umbrella in order to account for the ecological diversity protected areas have to support. For the first time, we apply the Probability of Connectivity index, currently the best connectivity index, to a migratory system, while accounting for species-specific autoecological requirements to determine habitat suitability. Guesstimates for species-specific disturbance distances are collected by an expert survey and used as a base for developing buffer areas.By working at these different spatial levels, our most important conclusions are that (1) in a wider geographical habitat network, Greek wetlands take an important position in upholding connectivity; (2) disturbance at the scale of wetlands can impact the connectivity of entire flyways; (3) the relative importance of nodes is maintained for directed and undirected approaches; and (4) although habitat availability has an important species-specific component, networks can be developed to sustain good connectivity for a combination of some species. With an additional sensitivity analysis we support the applicability of the Probability of Connectivity index while at the same time investigating the connectivity impact of various types of changes in the habitat network. |
