[7] On evidence, when staple prey populations decline or are locally scarce, Bonelli's eagle switch to being an opportunistic predator of a wide variety of birds.

These species are all conspicuously larger than Bonelli's and African hawk-eagles with differing proportions to their wings, tail and legs (in adaptation to their open country habits) and much darker coloured plumages.

Furthermore, the four other traditional members of the genus Aquila have been revealed to be a separate species complex despite showing superficial similarity to the golden eagle group, i.e. being relatively large and long winged with usually dark colouring.

The latter race is linearly smaller, and compared to other Bonelli's eagles tends to have more strikingly barred remiges and tail, the belly, thighs and crissum more boldly marked.

The adult's tail is grey with obscure darker brown thin bars, with a broad blackish subterminal band and creamy white tip.

[6][27] In flight, Bonelli's eagle is a largish raptor with a well projecting head and broad, long and somewhat square ended wings which are slightly pinched in at body with a little tapering at tips.

The sympatric species of honey buzzard tend to have bolder barring on the tail and underwings, broader dark trailing wing edges and all have no pale mantle patch or darker underwing-diagonals.

[6][24][37] An unlikely source of confusion is the northern goshawk (Accipiter gentilis), which is usually visibly smaller with much shorter wings, a slightly longer tail, different level flight style and many distinctive plumage characteristics.

[75][76] Wanderings include around 700 km (430 mi) north of their regular range in France near the coast of English Channel, far from their normal haunts in Regensburg, Germany and, probably both from the Italian island populations, to northwestern Italy and Slovenia.

[6][24][85] Usually, extensive garrigue-type habitat such as low bushes or more substantial vegetation such as scattered trees are a common feature of residential ranges but also at times even denser woodlands.

[87] Bonelli's eagles may additionally range into timbered plains or even virtually barren slopes or semi-desert, especially in areas such as Israel and India where moister valleys intersect with deserts.

[6][33][92] Bonelli's eagles also hunt in a quartering flying style relatively close to the ground (in a fashion reminiscent of a harrier) or patrols hillsides for prey activity.

In western Europe, it is considered something of a specialist predator on rabbits and partridges, though other birds such as pigeons, gulls and corvids sometimes are taken as much or more so depending on local prey population trends.

[99] In Spain, it was found that about three-quarters of studied floating juvenile Bonelli's eagles were hunting rabbits almost exclusively, apparently as they were easier to capture despite their larger size than bird prey.

[101][102] Other gulls are readily taken by Bonelli's eagles as well as wide diversity of other water birds, including rails, stone curlews, lapwings, sandpipers, tubenoses, cormorants and herons.

[24][25][103][114][115] Corvids, of a dozen or more species and up to the size of the 1.1 kg (2.4 lb) common raven (Corvus corax), are taken in considerable numbers in differing parts of the range.

[103] Corvids were the leading prey for Bonelli's eagles in Georgia, with the Eurasian magpie comprising 12.3% of the diet (though largely young were reportedly taken) and carrion crows (Corvus corone) making up a further 10.76%.

[96][99] In northwestern Africa such as Morocco, it was reported that the fat sand rat (Psammomys obesus), another rodent of similar size, was amongst the favourite foods locally for Bonelli's eagles.

[122] Other rodent species known in the diet of Bonelli's eagles have included other squirrels, gundis, assorted mice, voles, dormice and blind mole rats.

Relatively large adult specimens of ocellated lizard (Timon lepidus), at 228 g (8.0 oz) in mean body mass, made up 3.97% of the biomass and 7.05% by number in Catalonia, Spain.

Often the Portuguese nesting eagles used invasive Tasmanian blue gum (Eucalyptus globulus) (44.2% of the time) while a further 21.2% were on cork oak (Quercus suber) not to mention some that were placed on large shrubs, i.e. strawberry trees (Arbutus unedo).

Bonelli's eagles in India may also nest close to human habitations if disturbance is low, such as in Saurashtra and in Himalayan foothills, in the latter often in large chir pine (Pinus roxburghii) near villages.

On evidence, egg laying and hatching may grow more asynchronous when frequently interrelated outside stressors such as food supply, habitat disturbance and poor weather are applied, all of which may increase the likelihood of cainism.

[187] On evidence, the younger eaglets of Bonelli's eagles and other species in areas where threatened may too survive by human intervention, wherein they remove the chicks and either raise them in semi-captivity or introduce them to a new set of parents.

Perhaps the only factor preventing authorities such as the IUCN from uplisting Bonelli's eagle to a more severe status is due to lack of extensive research on their population in the Asian range.

[1][6] A bird survey of a large area of Uttarakhand, India where the species was historically present failed to find any signs of remaining Bonelli's eagles.

[202] In multiple parts of the range, certainly in western Europe as well as Cyprus, Bonelli's eagles face a high degree of persecution by hunters, gamekeepers and pigeon-fanciers.

[59][203] Habitat alteration and destruction (e.g. development of roads, intensified agriculture, irrigation of dry fields) in addition to reduced prey numbers and human disturbance in the nesting area are ongoing and increasing threats everywhere for this eagle.

[210] As reported by 2015, biologists in coordination with local authorities started to properly insulate dangerous powerlines in green areas in order to help converse this and other threatened birds.

[221] In further efforts to converse the species locally, Spanish researchers have provided supplemental feedings to these eagles, which may improve their odds of successfully producing young.