Diurnal raptors are also sometimes vulnerable to predation by Ural owls, including grey-faced buzzards ("Butastur indicus"), Eurasian sparrowhawk ("Accipiter nisus"), common kestrel ("Falco tinniculus") and even apparent adult northern goshawks. Thus the Ural owl, coupled with a very low known rate of natural predations, appears to occupy a similar position in the intraguild predatory hierarchy as the goshawk. In Finland, both smaller owls and diurnal raptors such as sparrowhawks and even buzzards appear to avoid nesting near Ural owls. In addition, Ural owls are known to have successfully have chased off actively nesting goshawks as well as European honey buzzards ("Pernis apivorus"), common buzzards ("Buteo buteo") and black kites ("Milvus migrans") in order to claim the nests for themselves. Despite their potential predation on smaller mesopredators, when nest boxes for European pied flycatchers ("Ficedula hypoleuca") were experimentally placed in the area of Ural owl nests, productivity lowered, and it is possibly because mesopredators were often attracted to the corresponding food base of the owls. On the contrary, experimental ground nests put out by researchers with random poultry eggs in central Finland were shown to be incidentally protected by the fierce presence of Ural Owls. In the Finnish ground placed almost directly under the Ural nest none at all were preyed upon, while in those placed away, 8.3% were predated, and those within experienced an average predation rate of 58.3%. At a great distance, at all ground nests were predated. The Ural owl generally pairs for life and maintains a territory for several years. Mate retention in Fennoscandia was found to have averaged 98-100% in males and 90-95% in females, making it amongst the most monogamous birds of prey of any order (or at least well-studied bird of prey species). Territories of Ural owls are on average about 3 times larger than those of tawny owls. In Sweden, about 3000 pairs of Urals are found in an area. In Finland, nests are usually somewhere between apart in wildland areas. Per Finnish data, the Ural owl had the second most nest found for an owl species from 1985-1989, with 901 nests second to the boreal owl with 2265 nests.