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.
White-tailed eagle
Known natural predators of white-tailed eagle eggs and nestlings include red foxes, martens and bears, especially if nesting in overly accessible rock formations, while wild boars have been recorded eating eggs and nestlings that’ve fallen out of the nest too early. Avian predation, overall a seemingly rare occurrence, of white-tailed eagle eggs and nestlings have been reported as crows, common ravens and western marsh harriers, which are likely to succeed in cases where nest attendance is low or if successful in driving away the parents via fierce mobbing. Furthermore, Eurasian eagle owls have been reported to prey upon "fairly large" nestlings of white-tailed eagle in nighttime ambushes. Many juveniles do not survive their first year post-independence. In the 1970s, an average of 56% banded first-year white-tailed eagles in Norway, Sweden and Greenland were found dead, most often having been shot. In eastern Germany, of 194 white-tailed eagles found dead between 1946 and 1972, of those where cause of death could be determined, 39% had been shot, accidents (especially powerlines) accounted for 6%, territorial disputes 7.5% and conservatively 13% were from poisoning. It is estimated that the survival of those that reach adulthood at 70%. Another estimate of average lifespan for those who reach adulthood is just over 12 years. Widely reported individuals have been found to live for 25 years or more, Another estimate of mean lifespan (presumably without persecution) is 21 years. At one point, the oldest banded white-tailed eagle known in the wild known lived for 27 years. However, a wild eagle of the species was subsequently recorded to life for 33.1 years. White-tailed eagles in captivity have lived for more than 40 years, though their exactly captive longevity record is not known.