Dietary biology of the Eurasian eagle-owl
In the Iberian peninsula, the Eurasian eagle-owl is part of a complex guild of predators that have evolved to survive mostly on European rabbits. Among this guild, golden eagles ("Aquila chrysaetos") were recorded per one study to rely on rabbits for 40% of the diet, the eagle-owl for 49% of the diet, the Spanish imperial eagle ("Aquila adalberti") for 50% of the diet, the Bonelli's eagle ("Aquila fasciata") for 61% of the diet and the Iberian lynx ("Lynx pardinus") for 79% of the diet. Elsewhere, the Spanish imperial eagle and eagle-owl are considered to outflank the golden and even the Bonelli's eagle as the most specialized avian predator of rabbits in the Iberian region. Other predators, such as common buzzard ("Buteo buteo"), northern goshawk ("Accipiter gentilis") black kite ("Milvus migrans") Iberian wildcat ("Felis silvestris tartessia"), red fox, stone marten ("Martes foina") and introduced Egyptian mongoose also prey heavily on rabbits in Spain, but are more generalized and less reliant than the above predators. All these powerful predators do not generally compete directly for food but conflicts may ensue over the rights to territories and nesting sites amongst the birds. Being nocturnal in activity, however, the Eurasian eagle-owl does not tend to compete as directly as do the three eagle species and even these are discreetly segregated by habitat preferences, the goldens preferring open, steep cliffs, the Bonelli's favoring densely vegetated areas mixed with rocky spots and the imperial favoring relatively flat open woodlands. Among these eagles, the golden eagle tends to have the most similar habitat preferences to the Eurasian eagle-owl and across a broad band of overlapping distribution, the two are considered nearly ecological equivalents by day and night. However, good-sized female golden eagles are up to twice as heavy as an average eagle-owl, so seem to have a considerable advantage in size and power. Conversely, to support their large size and large territory needs, the golden eagle cannot survive on small and diverse prey nearly as successfully as the eagle-owl. Among the Iberian peninsula rabbit-eating guild, the species with wider ranges, the eagle-owl and the golden and Bonelli's eagles, have had some degree of success living off of alternate prey following the devastation of the rabbit population due to rabbit haemorrhagic disease. The two rabbit predators endemic to Iberia, the Iberian lynx and Spanish imperial eagle, have been devastated by the reduction and other causes and both are threatened species today.
Dietary biology of the Eurasian eagle-owl
Hedgehogs often comprise a fairly significant portion of the prey taken by Eurasian eagle-owls, both in numbers and biomass. At least eight species of hedgehog have been predated. The European hedgehog is often one of the most prominent prey species in eagle-owl diet studies from Europe, and was recorded as the most numerous prey species per researchers in parts of Denmark, Switzerland, Austria and south Germany. With an average weight of , the European hedgehog can comprise a very large portion of the biomass. A study of the Bavarian region of Germany, the European hedgehog (the main prey species) made up 41.7% of the prey by number and 52.1% of the biomass, the maximum representation of hedgehogs known in Europe. Other members of the "Erinaceus" genus are also locally regularly taken, as is the Daurian hedgehog ("Mesechinus dauuricus") in Mongolia. Studies from Greece and the Czech Republic found that the northern white-breasted hedgehog ("Erinaceus roumanicus") was the leading prey species. Unidentified "Erinaceus" hedgehogs almost totally dominated the diet of eagle-owls in Stavropol, Russia, making up 70.9% of the food, only the European rabbit has been found as more significant at the genera level by number in a given dietary study. Studies from both Syria and Kazakhstan showed that the long-eared hedgehog ("Hemiechinus auritus") was the most significant prey, making up 25.3% and 33.6% of the prey remains, respectively. After killing hedgehogs, the Eurasian eagle-owls peel the prickly skin off their backs before consumption, frequently resulting in up to dozens of hedgehog backs being found around nests. Moles and shrews are readily hunted but are usually only a secondary portion of the diet. Eurasian eagle-owls have been recorded hunting the smallest mammal on earth (by weight) the Etruscan shrew ("Suncus etruscus"), as well as the largest mole on earth, the Russian desman ("Desmana moschata"). From the smallest shrew to the heaviest hedgehog, the Eurasian eagle-owl has been verified to hunt the full size range of insectivores. They've also attacked bats of every size available, from the smallest European bat, the common pipistrelle ("Pipistrellus pipistrellus"), to the largest species there, the greater noctule bat ("Nyctalus lasiopterus"). In the Sikhote-Alin range of the Russian Far East, bats were found to comprise 5.9% of the remains and, of five local owl species, the Eurasian eagle-owl was the most regular predator of bats in the area.