Eurasian hobby
Although other birds of prey are seldom caught, given that they are wary, fast and can defend themselves well, the white-tailed eagle can be characterized as an opportunistic predator of such birds. Indicating that they are regarded as a threat to raptors is that they are frequently mobbed by a wide range of raptor species when displaying active flights, to a similar regard that the perhaps more aggressively predatory golden eagle is. Given the difficulty of this prey type, white-tailed eagles are likely to attack other birds of prey when the victims are distracted, whether by migration on windy days, nesting duties or when trying to capture their own prey, are previously injured or they may even capture one while the raptor tries to mob the eagle. Certainly, nestlings and fledglings can certainly comprise a large fraction of the birds of prey caught as well as adult ones. Other accipitrids they are known to have preyed upon, in increasing order of size are the Eurasian sparrowhawk ("Accipiter nisus"), western marsh harrier ("Circus aeruginosus"), black kite ("Milvus migrans"), European honey-buzzard ("Pernis apivorus"), common buzzard ("Buteo buteo"), northern goshawk, red kite ("Milvus milvus"), lesser spotted eagle ("Clanga pomarina") and eastern imperial eagle, in addition to osprey. Non-accipitrid raptorial birds, these more likely restricted to fully independent birds due to their less conspicuous nests, known to fall prey to white-tailed eagles include Eurasian pygmy owl ("Glaucidium passerinum"), boreal owl ("Aegolius funereus"), Eurasian hobby ("Falco subbuteo"), long-eared owl (Asio otus), northern hawk owl ("Surnia ulula"), short-eared owl ("Asio flammeus"), peregrine falcon ("Falco peregrinus"), snowy owl ("Bubo scandiacus") and Eurasian eagle owl ("Bubo bubo"). Accipitrid prey size ranges by body mass ranges from for a sparrowhawk to in the imperial eagle and that of non-accipitrid raptors ranges from for the pygmy owl to for the eagle owl and apparently both imperial eagles and eagle owls that were caught were adults. As true apex predators, healthy adult white-tailed eagles have no known natural predators.