The Black-headed Yellow Wagtail (Motacilla flava feldegg) has shown a clear tendency to expand its breeding range in the period 1830-2015, with an accentuation of the phenomenon during the second half of the twentieth century. Expansion northwards has been favoured by climate change and is characterized by alternating phases of jump dispersal and subsequent diffusion within the limits thus achieved. In the Balkans and in western Europe, jump dispersal occurred mainly in the late nineteenth century and mid-twentieth century, allowing the subspecies to reach the 48th parallel north. In the eastern portion of its breeding range, however, jump dispersal mainly took place in the last decades of the twentieth century and in the early part of the twenty-first century. In Europe (especially in the oriental sector) and in Asia, the northern edge of the range is defined with good approximation by the 20°C isothermal of July. In Europe, there has been a shift in its distribution range to the west and the establishment of a new, progressively more import migration route leading the subspecies from Africa to Europe across the Strait of Gibraltar. Concurrently, more and more sightings of the Black-headed Yellow Wagtail have been reported in northern European countries. In the Middle East, expansion to the southwest in Syria, Israel, Lebanon and Jordan has diffusive characteristics and exploits almost exclusively natural environments. In contrast, nesting in the southernmost parts of the Arabian Peninsula is determined by human activity, in particular by the irrigation of fields for the production of fodder, demonstrating the potential of the subspecies to expand further south. In this case, the limiting factor is certainly the lack of a suitable environment, due to the strong prevalence of a hyperarid climate. In central Asia, especially in the catchment area of the Aral Sea, the spread of feldegg has been favoured by the irrigation of the land for agricultural purposes. In the far eastern edge of its distribution range, no particular expansive or recessive movements have been observed.
biotic and abiotic factors, climate change, northward expansion, Europe, Asia