Dietary biology of the Eurasian eagle-owl
In rare cases, other predators may kill a Eurasian eagle-owl. In Europe, there is one case of a white-tailed eagle killing an eagle-owl and there are at least four known incidents of eagle-owls being killed by golden eagles. Also, an eagle-owl was found among the prey remains at a golden eagle eyrie in Mongolia. An eagle-owl was also found amongst the prey in the nest of steppe eagles ("Aquila nipalensis") in Altai Krai, Russia. In 2016, a large female subadult Bonelli's eagle ("Aquila fasciata") apparently preyed upon a three-year-old male Eurasian eagle-owl in Spain. Pine martens ("Martes martes") and stone martens ("Martes foina") are opportunistic nest predators. Although martens could probably reach most eagle-owl nests due to their agility and climbing abilities, they probably will attack nests when disturbance or low food supply result in lower nest attendance by the parent owls. Cases where nests have atypically been accessible on foot (for both humans and wild predators) have resulted in Eurasian eagle-owl nests being predated. Eurasian badgers, wild boars and raccoon dogs and raccoons, the latter two both where non-native in Germany, have also reportedly preyed on nests that they can access. In coastal areas of Spain, red foxes were reported to have preyed on four eagle-owls, including one unsexed brooding adult, at nests found to be reachable on foot by researchers. Cases of red foxes killing Eurasian eagle-owls at nests have reported elsewhere albeit very rarely, normally the eagle-owl is a greater danger to the foxes (and many of its other nest predators) than vice versa. In May 2017, a red fox was filmed killing two chicks and raiding the larder of an eagle-owl in Denmark.
White-tailed eagle
This eagle breeds in northern Europe and northern Asia. Their European range extends to as far west as southeastern Greenland, northern and eastern Iceland, and the reintroduced populations in some areas of Ireland and Scotland, particularly conserved coastal spots. In mainland Europe, often isolated outposts remain in coastal and western Norway (broadly), northern and southwestern Finland, eastern Sweden, southern Denmark (and some spots in the north), islands of the Baltic Sea, western Austria, northeastern Germany, northern and eastern Poland, the Czech Republic, much of the east Baltic countries, the non-montane areas of the Ukraine, eastern Slovenia, central and southern Hungary (and adjacent northeastern Croatia), very sporadically in Greece, the Danube sections of Romania and Bulgaria to the Black Sea and western and eastern Moldova. In Asia Minor, it only remains as a breeder in very sparse and small pockets of Turkey and Georgia, taken as a region there is likely to be fewer than 30 breeding pairs in this region. In the Middle East, the white-tailed eagle may still be found breeding only along the southern coast of the Caspian Sea in northern Iran and southwestern Turkmenistan. Discontinuously, they are found as residents in Kazakhstan where they live in a long strip of the southern part of the country starting at the Aral Sea and the northwestern portion (but not, as far as is known, breeding in the Kazakh part of the Caspian Sea coast). The only country in which the white-tailed eagle is found over a continuous and extremely large area is Russia. The species is found very broadly everywhere in Russia from European Russia in the west to the Bering Sea in the east, only being fully absent as a nester as far as is known from the high Arctic regions and a section bordering westernmost Kazakhstan, although it breeds to south of this in the Russian coastal part of the Caspian Sea. Their northern limits occur in Russia to the Ob river to 70 degrees north at the mouth of the Yenisei River and on the Gydan and Yamal Peninsulas, to the Kolyma, Indigirka and Lena rivers to above 72 degrees north, even to 75 degrees north on the Taymyr Peninsula. They are said to be common around the White Sea, reportedly even the most abundant bird of prey locally and found both on coasts and inland lakes, although breeding rates are low due to the frigid weather. From Russia, breeding populations spill somewhat into northernmost Mongolia, extreme northwestern China and northern North Korea. The white-tailed eagle also breeds on Sakhalin Island, the Kuril Islands and Hokkaido, the northernmost island of Japan.