Eurasian Eagle Owl Bubo bubo (Linnaeus, 1758)
It’s hard to imagine a Ukrainian who doesn’t know Eagle Owl, one of our bigger owls. This bird appears in a number of fairy tales and legends. But a few people know that Eagle Owl lives nearby though is rarely seen due to crepuscular way of life. But who is this bird?
Let’s start at the description of appearance. The total size of the owl is 60-75 cm, the wingspan is more than 1.5 m but slightly less than 2 m. The adult birds weigh 1.5-4.2 kg. The plumage of the upperparts is dark brown with buff and whitish spots. The underparts are ochre-coloured and marked by dark brown streaks. ‘Ears’ are comparatively big & dark with light edge, chin and throat are white, tail is dark brown with whitish streaks, bill is dark grey, eyes are deep orange. Legs are feathered, claws are large and massive. Male and female share virtually identical colouration but female is larger and heavier.
Eagle Owl is a widely distributed species. Its range encompasses almost all Eurasia and North Africa but in Ukraine it is rather fragmented. One portion of the range is in Polissya region and Carpathian mountains where a European forest-dwelling sub-species breeds. Another subspecies breeds in Eastern Ukraine, basically, in Lugansk region. These birds are smaller and differ in life history.
Adult Eagle Owls are sedentary. The ‘song’ of a male may be heard at breeding sites already in late winter. These ‘oohu’ calls are quite loud and spread for at least one kilometre. The breeding grounds of Eagle Owl are hard-to-reach forests surrounded by bogs, rock outcrops in mountains and steep slopes in chalk and clay ravines in steppe zone. Eagle Owls don’t build nests. Small depression under the ledge of a rock, below the crest of ravine, under exposed roots in a forest or on a slope is what may be called a nest. Female lays 2, 3, or rarely 4 white eggs of size of a chicken egg early in spring. The incubation period lasts about a month. Owlets stay in a nest for one month more, and then wander in its outskirts for 1 to1.5 months being fed by the parents. At this time owlets have not grown their feathers and are not capable of flight. Therefore they are very vulnerable to predators.
The Eagle Owl’s diet includes birds and mammals of small and medium size. The prey may be rodents, or hedgehogs, or even red fox cubs. The range of bird prey is wide and includes both small passerines and comparatively large birds e.g. birds of prey and owls. More often there are species of crepuscular or nocturnal habits. But due to its general rarity Eagle Owl doesn’t pose a serious threat for the species of local fauna.
Despite their rarity, many Eagle Owls perish due to human impact. Hunters who shot these birds illegally pose the greatest threat. Sometimes nests are taken by herdsmen or their dogs, or are lost in human-induced fires in spring. Besides, some nests or broods are destroyed by natural enemies, mainly, as a result of predation by foxes and wolves. There are some evidences of the losses of birds at electric power lines, under the wheels of trains or cars. All these factors reduce the numbers of the species. We know many cases of abandonment of breeding sites for a long time after one of a pair was shot, despite the successful breeding in previous years. At some sites no new pairs are formed because of regular disturbance by humans.
Text by V.V. Vetrov