Environmental factors determining the establishment of the African Long‐legged BuzzardButeo rufinus cirtensisin Western Europe

Abstract

Winters have become warmer under the impact of climate change, which has modified the phenology as well as the distribution ranges of birds. The African Long‐legged Buzzard Buteo rufinus cirtensis has recently colonized Europe via the Strait of Gibraltar. We aim to explain the native distribution of this species and to predict favourable areas in newly colonized parts of Europe using geospatial modelling to identify the most influential factors in this process. We applied the favourability function, a generalized linear model describing environmental favourability, for the presence/absence of breeding areas in northern Morocco and the southern Iberian Peninsula, according to a set of variables describing climate, topography, human activity, vegetation and purely spatial trends. A model was built using some known breeding sites in northern Morocco, and was used to forecast future suitable breeding areas in Europe. A second model was built with the available data for northern Morocco and Europe to explain the current distribution of breeding sites. Both models were assessed according to discrimination, calibration and parsimony criteria, and the influence of each factor was analysed using variation partitioning. We conclude that the Iberian Peninsula could provide new suitable areas for the species and facilitate its northward expansion. This result, together with the increasing number of records available, suggests that this species could soon spread throughout Europe. Steady temperatures and abundant but seasonally distributed precipitation showed the strongest predictive power in the models. This indicates a close relationship between the species’ distribution and climate in the study area, and suggests that this species finds its most favourable environments in the Mediterranean biome. Topography and vegetation, specifically cliffs and woods near hunting zones, point to a fine‐scale habitat selection for breeding. As the case of the African Long‐legged Buzzard is not a unique event, our results may be useful to determine whether a northward expansion of the Mediterranean biome could be followed by distribution shifts of bird species that have so far been restricted to Africa.

Fuzzy sets allow gaging the extent and rate of species range shift due to climate change

“…Consequently, the favourability model can be rightly considered to be a climatic favourability model. The requirements of this buzzard are matched with Mediterranean climatic conditions 2 as shown by the concentration of highly favourable areas for breeding in the Mediterranean basin and the generally low climatic favourability values in the European continent, which are especially low in the Alps, the Caucasus Mountains, and the British and Norwegian coasts. The main favourable climatic conditions included in our model are low precipitation during summer, low temperatures during the wettest season and stability in daily temperatures (Table 1 ).…”

“…Environmental, biological, historical, and anthropogenic factors affect the distribution of species in space and time 1 . However, climate seems to be the most relevant factor for several taxa at large scales [2][3][4][5][6] . Throughout the last century, and especially over the last few decades, there have been global alterations leading to a warmer climate 7 with widespread effects on biological systems [8][9][10] .…”

“…These changes are putting into contact two faunas in the European part of the Strait of Gibraltar, entailing changes in communities that are leading to new ecological interactions in this region 35 . The southern part of the Iberian Peninsula is a suitable place for colonization by different African bird species 36 , for which it is beginning to act as a focal point in the colonization of Europe 2,37 . In order to forecast these distribution ranges, more information is needed on whether these species are expanding or shifting their distributions, the spatial and temporal disequilibrium between the species ranges and their climatic favourability, the latitudinal rate of their change in distribution range, and whether these rates are expected to increase, decrease or remain constant in the future.…”

“…1 a) 38 – 41 , the Atlas long-legged buzzard ( Buteo rufinus cirtensis ), has recently colonized Europe 19 . Chamorro et al 2 conducted a biogeographic study of this subspecies and showed that climate is the most important factor affecting the distribution of the Atlas Long-legged Buzzard, suggesting that climate change is the main driver of this biogeographic change. This assessment was based on the notion of climatic favourability, a typical fuzzy concept whose theoretical foundation rests on fuzzy set theory rather than on niche theory.…”

The Strait of Gibraltar as a metaphor for the upcoming IBS meeting

“…The Strait of Gibraltar is also a pathway that connects Mediterranean and Atlantic waters and Europe and Africa, all of which modify local and regional populations. This transition zone is thus a significant area for monitoring marine biological invasions of species of tropical Atlantic origin into the Mediterranean, as well as modification in distribution of plant and animal species and changes in migration habits of terrestrial animals, mainly birds and insects, due to climate change (Altamirano et al 2008, Chamorro et al 2017.…”