Southern Europe is becoming favourable for African birds: anticipating the establishment of a new species

Abstract

Background: The current modification of species distribution ranges, as a response to a warmer climate, constitutes an interesting line of work and a recent challenge for biogeography. This study aimed to determine if the climatic conditions of southern Europe are adequate to host a typical African species, the House Bunting, which is registered regularly during the last years, still in low numbers. To this end, the distribution of the species in its native range was modelled, both in the present and in future climate scenarios, using its current breeding distribution areas and a set of environmental variables. Results: The results showed that the southern half of the Iberian Peninsula exhibits high values of favourability to host this African species for the current climatic conditions. Furthermore, future forecasts indicated an increase in favourability for this area. The favourable areas we detected in the south of the Iberian Peninsula are already regularly receiving individuals of the species. These observations are very likely vagrant birds dispersing from recently colonised breeding areas in northern Morocco, which may indicate a continuous process of colonisation towards the north, as has occurred during the last decades in Northern Africa. Conclusions: We cannot anticipate when the House Bunting will establish on the European continent because colonisation processes are usually slow but, according to our results, we predict its establishment in the near future. We have also identified those areas hosting favourable conditions for the species in Europe. These areas are a potential focal point for the colonisation of this and other African birds if the climate continues to warm.

Evaluating the expansion of African species into Europe driven by climate change

“…Additionally, certain species, such as the House Bunting (Emberiza sahari; López- Ramírez et al, 2023) and the Rüppell's Vulture (Muñoz et al, 2024), initiated breeding in 2023, with other species expected to start breeding soon. Climate change is expected to increase both temperature and the frequency and duration of heat waves, as well as reduce the number of cold nights and the annual mean precipitation in many mid-latitude regions (IPCC, 2022).…”

“…The effect of prevalence on the probability values was therefore removed, thus obtaining favourability values by applying the favourability function (Real et al, 2006). More detailed discussions of the procedure have been published previously (Chamorro et al, 2020;García-Carrasco et al, 2021;López-Ramírez et al, 2023). The term 'favourability' refers to the degree, ranging from 0 (minimum favourability) to 1 (maximum favourability), to which the environmental conditions are propitious for a species to breed (Acevedo & Real, 2012;Muñoz et al, 2015), with F = 0.5 being the threshold separating favourable from unfavourable areas.…”

“…In the case of birds, a short-distance expansion of African species' range towards the north represents a major step in biogeographical terms, as a new continent would be reached and colonised. In recent years, the south of the Iberian Peninsula has been acting as a focal point in the process of African birds colonising Europe (Chamorro et al, 2017;Elorriaga & Muñoz, 2010;Ramírez et al, 2011), which makes it an area of great value for studying the effect of climate change on species distribution (López-Ramírez et al, 2023). This is not exclusive to the Mediterranean basin, as a number of species typically distributed in southern Europe have also been expanding their distribution ranges towards the north (Knaus et al, 2018;Stiels et al, 2021).…”

“…Favourability models have proven to be useful tools for identifying new potential areas for the arrival and establishment of new individuals in the near future(López-Ramírez et al, 2023;Muñoz & Real, 2006;Pulido-Pastor et al, 2018). In the present study, we constructed climatic favourability models to analyse the responses of species to climate change by identifying potentially favourable breeding areas in the European continent for nine species of African birds that are moving northwards.…”

“…It is necessary to consider that these species face a biogeographical barrier, the Mediterranean, which may slow the process of colonisation. Regardless, several African species have recently started to breed in southern Europe(Cabrera, 2022;Elorriaga & Muñoz, 2010;Navarrete, 2022;Prieta, 2022), and there has been an increasing and regular number of observations of other species that may become established soon(López-Ramírez et al, 2023). The results for the period 2041-2060 are based on the future model with the lowest uncertainty and this future projection turns out to be one of the most optimistic, as it is based on the results of the Representative Concentration Pathway 2.6.…”