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Distribution and population
Bonelli's eagles are distributed along most of Southern Portugal, while in the North and Central parts of the country their range is largely restricted to the international border regions of the Douro and Tagus rivers. Dense clusters exist in the Northeast, as well as in the low mountainous areas of the Southwest and in the cereal pseudo-steppes of the Southeast. These Southern nuclei hold ca. 70% of the Portuguese population of this species, estimated to be around 100 breeding pairs. Within the remaining distribution area - coastal limestone formations of the Portuguese Estremadura, the international course of the Tagus, the middle stretches of the Tagus, Sado and Guadiana river basins - the species occurs in small clusters or shows a more scattered pattern.
Settlement areas
Before reaching sexual maturity at its 3rd year of age, Bonelli's eagles go through a dispersive phase, when they use areas free of breeding territories and with abundant, most often in open or sparsely forested terrain. These are known as settlement areas.
The main pre-adult settlement areas in Portugal are located in the Southern plains, above all in the same region which includes the Southeast pseudo-steppe breeding territories. Studies developed in those settlement grounds reveal low mortality of non-breeding birds, probably due to low density of power lines, infrequent human persecution and high prey availability within Special Hunting Regime areas of that region. Most individuals born in Southern Portugal use this region before reaching sexual maturity.
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