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.
European polecat
The European polecat's diet consists of mouse-like rodents, followed by amphibians and birds. Its most frequent prey item in the former Soviet Union is the common vole and rarely the red-backed vole. In large river floodlands, water vole are common prey. In spring and winter, amphibians (especially grass frogs and green toads) become important food items. Selective predation on male frogs by the polecat decreases the occurrence of polyandry in frog populations. However, because amphibians have little calorific value, the polecat never grows fat on them, no matter how many it consumes. In Central Europe, the diet in winter months is dominated by birds including quail, grey partridges, grouse, chickens, pigeons and passerines. Seasonal changes in the activity rhythm is synchronised with the activity of the main prey. Some species only rarely preyed upon by the polecat include European hedgehogs, asp vipers, grass snakes and insects. In the British Isles, it commonly kills brown rats and European rabbits, and is capable of killing larger prey, such as geese and hares. One polecat was reported to frequently wait at a riverbank and catch eels, which it took back to its burrow. The polecat feeds on eels mostly during lengthy frosts when eels, unable to breathe air at regular intervals because of the ice, congregate at breathing holes. Unlike the stoat and weasel, the polecat readily eats carrion, including that of large ungulates. The European polecat hunts its prey by stalking it and seizing it with its canine teeth, killing the animal with a bite to the neck. This killing method is instinctive, but perfected with practice. The polecat sometimes caches its food, particularly during seasonal gluts of frogs and toads. Sometimes, the polecat does not kill these, but bites them at the base of the skull, thus paralyzing them and keeping them fresh for later consumption. Although they are normally shy around humans, naturalist Alfred Brehm in his "Brehms Tierleben" mentions an exceptional case in which three polecats attacked a baby in Hesse. During the winter period, when live prey is scarce, the European polecat may raid beehives and feed on the honey.