The Bonelli's eagle is a large bird of prey from the Accipitridae family. Its breeding areas are very specific and include southern Europe, North Africa, the Eastern Mediterranean (including Israel), South Asia and Indonesia. A study led by researchers from the University of Granada in Spain along with researchers from Alcalá University in Spain have made some surprising discoveries.
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The Bonelli's eagle near the Spain-Portugal border
(Photo: Pascal De Munck, Shutterstock)
"The Bonelli's eagle is a 'newcomer' to Europe. This species probably began establishing itself in the Mediterranean basin around 50,000 years ago. In contrast, others, like the golden eagle (A. chrysaetos), have been present here much longer, as fossil records attest," explains Professor Marcos Moleón Paiz, from the Department of Zoology at University of Granada.
According to the study, spatial analyses show that Bonelli's eagle is significantly disadvantaged during cold climatic periods, unlike the golden eagle. "During the last glacial period, the Bonelli's eagle could only find refuge in warm coastal areas, precisely where its oldest fossils have been found." Eva Graciá, a professor of Ecology at The Miguel Hernández University, notes that "genetic analyses confirmed that around the last glacial maximum, the Mediterranean population of Bonelli's eagles must have been formed by few individuals."
According to Moleón: "After testing several alternative hypotheses, all pieces of the puzzle indicated that the early European settlers of our species (Homo sapiens) played a fundamental role."
This study collected and analyzed the most comprehensive information on the competitive interactions between Bonelli's eagles and golden eagles today. It has allowed the researchers to confirm that, in this relationship, the golden eagle is the dominant species and the Bonelli's eagle the subordinate species. The results showed that Bonelli's eagles can only survive where golden eagles are scarce, mainly in highly humanized areas.
"Our mathematical models indicated that if we were able to eliminate all golden eagle pairs in climatically favorable areas, we would expect a strong increase in the number of Bonelli's eagle pairs, but not visa versa," the researchers explain. The study also states that golden eagles can kill Bonelli's eagles and usurp their territories, which does not happen the other way around.
Golden eagles are less tolerant of humans than Bonelli's eagles. The authors hypothesize that, with the arrival of the first anatomically modern humans in Europe, some of the golden eagle territories closest to human settlements were abandoned, and these 'vacant' territories began to be occupied by Bonelli's eagles from the Middle East.
In short, Bonelli's eagles could not have established themselves in the Mediterranean before the arrival of the first Homo sapiens because the competitive pressure exerted by golden eagles and other species would have been too overwhelming.