Bonelli's Eagles' Movements Shaped by Their Birthplace
A new study has shown that desert-born birds roam far and face greater risks, while Mediterranean birds stay closer to home.
Tracking the lives of desert and mountain eagles
A new study has uncovered striking differences in how young Bonelli’s Eagles Aquila fasciata move, settle and survive depending on where they are born. Using GPS transmitters, researchers followed 55 juveniles hatched in Mediterranean, semi-desert and true desert regions of the southern Levant – revealing that birthplace strongly shapes how far they roam and where they ultimately live.
Published in Ornithology by Asaf Mayrose and colleagues, the research tracked birds over several years as they left their nests and explored landscapes across Israel, Jordan, Sinai and beyond. Desert-born eagles travelled the farthest, often crossing the Sinai, the Arabian Peninsula or even reaching the Sahel, while Mediterranean and semi-desert birds stayed closer to home.
From the olive hills to the open desert
Natal dispersal – the journey from where a bird hatches to where it first breeds – is one of the riskiest and least-understood stages of a raptor’s life. For the region’s small and fragmented Bonelli’s Eagle population, this stage is vital for maintaining gene flow and recolonising lost territories.
The aridity of an eagle’s natal area was a powerful predictor of behaviour. Mediterranean and semi-desert birds tended to disperse shorter distances, largely within Israel or nearby regions, while desert-hatched birds routinely travelled hundreds – sometimes thousands – of kilometres south. Some even reached sub-Saharan Africa, skirting the Red Sea or crossing narrow sea gaps via islands such as Tiran as “stepping stones”.
Habitat imprinting and fidelity to birthplace
Throughout their journeys, the eagles sought landscapes with rainfall similar to their natal areas – a pattern consistent with natal habitat preference induction. Individuals from arid origins spent most of their time in low-rainfall zones; Mediterranean birds selected wetter, greener regions.
When they eventually settled to breed, most (10 of 11) recruited within the same climatic zone as their birthplace. The single exception – a desert-origin female settling in a Mediterranean territory – occurred at a site with repeated female losses to electrocution, hinting that territory vacancies may also steer settlement decisions.
Life and death on the wing
Survival differed by origin. Apparent survival was highest for Mediterranean birds and lower for semi-desert and desert birds. Electrocution was the leading confirmed cause of death, responsible for nearly half of known mortalities, particularly within Israel where power infrastructure is dense.
Desert-born birds faced a different threat profile due to their long-range movements. Many deaths occurred outside Israel – especially in the Sinai Peninsula, identified as a mortality hotspot with multiple suspected persecution cases.
Why some young eagles linger while others leap
Mediterranean eagles tended to leave their parents earlier, while desert-hatched birds delayed dispersal – a pattern consistent with the ontogenic switch hypothesis, which posits longer learning periods in harsher environments. Males dispersed earlier but travelled shorter distances than females.
Together, these results show how early-life conditions shape the strategies young eagles use to survive. A chick raised in a dry canyon faces different challenges and learns different cues than one from a wetter hillside – and those experiences echo through its dispersal choices.
Conservation implications: corridors, cables and cooperation
With only around 25 breeding pairs in the Levant and the species regionally Critically Endangered, protecting breeding territories alone is not enough. The study highlights the need to safeguard dispersal corridors and temporary settlement areas that sustain juveniles across years.
Powerline insulation remains a top priority to curb electrocutions, while cross-border cooperation is essential to address persecution along transboundary routes. Effective conservation cannot stop at national boundaries – these eagles connect landscapes and countries.
Born of the land, shaped by its limits
The landscape that nurtures each eagle helps dictate its destiny. Those born in lush Mediterranean valleys often stay close; those hatched under desert skies may cross continents. Understanding these innate movement patterns and risks offers a stronger foundation for conserving one of the region’s emblematic raptors – and for keeping Bonelli’s Eagles in the skies of the Levant for generations to come.
October 2025
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