The eagle owl (Bubo bubo), the largest of the owls living in Poland, can commonly be found in zoos, where it attracts visitors by its specific appearance. It has also become popular owing to literature (e.g. Dziady by A. Mickiewicz) where it was used to create the sense of mystery and dread. However, hardly anyone had a chance to meet an eagle owl in its natural environment - or at least to hear its night call - as in our country the bird remains an ornithological curiosity that lives in secluded areas and leads a secret, night life. The eagle owl is one of the largest birds in Poland - its wingspread ranges between 160 and 188 cm, its body length between 60 and 75 cm, the males weigh between 1.5 and 2.8 kg and the females between 1.7 and 4.2 kg. Its figure, however, seems more impressive, as the soft and abundant plumage does not stick to its body, which makes the silhouette downy. Its plumage is brown and red with dark spots. Long feathers on the top of the head resembling ears, ruffled and smoothed in various ways, are the eagle owl's distinctive feature. The bird's large vivid orange eyes also attract attention. Females and males differ in size - the former being slightly larger than the latter - which is typical of many birds of prey.

As regards zoological taxonomy, the eagle owl belongs to the order Strigiformes and, within this order, to the worldwide-spread family Strigidae comprising approx. 170 species. Its closest relatives include 13 species of the same Bubo genus, which mainly occupy the territory of Africa and South-East Asia. None of them can be found in Europe whereas in North America lives a very similar Virginian eagle owl, Bubo virginianus. Our eagle owl lives in a greater part of Europe, in a moderate climate of Asia up to China and North Africa. The species is not numerous anywhere and in some regions (eg. in Northern France, Belgium and the Netherlands) it has become totally extinct.

The population of eagle owls in Poland has been estimated at approx. 270 pairs. The largest concentrations can be found in the woods of Pomerania and Northern Wielkopolska, Northern Podlasie, Polesie Lubelskie, the Carpathian Mountains and Silesia. Eagle owl does not live in any part of the central Poland lowlands although once it used to be quite common.The eagle owl inhabits unbeaten lowland or mountainous forests, preferably near open areas such as water, meadows and marshland. In Poland, the eagle owl is a sedentary bird. It does not migrate in winter and remains on the same territory throughout the year though in countries with harsher climate it undertakes seasonal migrations. The eagle owl is active at night and spends the days hidden in thick branches or shadowy rock curves. However, the eagle owl can see very well and move freely, for instance when scared, also during the day.

Like other owls in Poland, the eagle owl is a typical bird of prey. It hunts both small animals including mice, voles, hedgehogs, birds of a tit size, frogs or large insects and much bigger prey such as ducks, herons, hares or even young foxes and deer. The eagle owl predominantly hunts in glades, wood-neighbouring meadows, marshland and waterside areas. The bird hunts by watching the area from a tree or a rock, or flying noiselessly above. A pair of eagle owls without their offspring needs approx. 200 kg of prey a year to feed themselves, which they hunt in the hunting territory they guard - up to 4 km in the summer and up to 7 km in the winter.

The presence of those birds (it is usually a pair of eagle owls occupying a given area) can most easily be identified by a specific call, which can most frequently be heard in early spring and autumn at dusk and dawn. The male mating sound is like a deep oo-hu (often repeated a few times) and seems not too loud at close quarters but it spreads across a large distance. The female responds in a similar manner but the pitch of her sound is higher and clearly divided into two syllables. The presence of an eagle owl is also marked by the so-called pellets. Like other owls, the eagle owl throws up hard and undigested parts of their prey (bones, hairs, claws, beaks and scales) in the form of pellets, which are clearly larger than those of an ordinary tawny owl inhabiting the woods, and their content shows what the prey was.

The eagle owls team up for many years, usually until one of them dies, and remain in the same area if they find the conditions favourable. Those birds do not build the nests themselves. During the hatching season, they use the nests of other big birds (e.g. buzzards or black storks), nest in crevices between rocks or simply on the ground covered by trees, thick branches or brushwood. At the end of March or at the beginning of April the female lays 2-4 white and almost round eggs hatched over 31-37 days while the male provides food. The male continues to perform this task during the period immediately after the nestling has hatched while the female warms it and divides food. The eagle owl is an extremely careful bird. If a pair is bothered in their nest they simply abandon it even if the nestling is already there. Young eagle owls leave the nest when they are approx. a month and a half old but they are unable to fly for the next dozen or so days. They stay close to the nest during this period. They become fully independent approx. five months after they have hatched; i.e. at the end of summer. They start their own families when they are two or three years old. The longest recorded lifespan of the eagle owl in the wild stands at 21 years. In captivity, they lived until they were 60. Still at the beginning of the 19th century, the eagle owl was quite common in the entire country, also in Masovia and other parts of central Poland where it cannot be seen today. At the beginning of the 20th century, it could only be found in the large woods of Eastern Poland and in the mountains. Shrinking or fragmentation of woods as well as intensified forest economy, which deprived the eagle owls of their habitats, contributed to their disappearance. Another, perhaps a more significant reason for the bird's extinction in a greater part of the country, was its persecution by man. It was deemed a pest by the hunters and combated using all methods available including killing the birds next to their nests or damaging the hatching. The so-called hunting with an eagle owl, using the nestling stolen from nests and brought up in captivity to serve this purpose, became a common form of entertainment. The hunters used the reaction of most of the forest birds and the birds of prey which, seeing (any) owl, fly towards it and harass it by screaming. An imprisoned eagle owl was placed in an uncovered place and thus enticed birds proved an easy prey for a hidden hunter. The eagle owl used as an enticement was often hurt or killed, so it was replaced with another one. This hunting method was used in Poland until the 1960s. Today, the eagle owls most frequently die after they have hit overhead wires and vehicles or after they have been electrocuted by power lines.

After the eagle owl was placed under strict species protection following WW II, its number in Poland continues to grow slowly but it is still on the list of the species endangered with extinction. Apart from the direct protection of the birds and their hatching, special protection zones around their nests have been introduced - the entry is prohibited within 200 m of their nests during the hatching season (from February to July) and no forest works or other activities likely to bother the nesting birds are allowed within 500 m. In some Western European countries, where the population of eagle owls has decreased like in Poland, the birds bred on the farms are placed in adequate environment. Those attempts have resulted in the reconstruction of population in many areas, including Germany, despite the fact that the birds from the farm find it difficult to adapt to wildlife. The birds have been settled in a similar manner in the Wolin National Park and a pair of eagle owls has remained in the Uznam Island most probably owing to such efforts.

It seems that in Poland and in the rest of Europe, the eagle owl has its worst time behind it. However, a lot of time and work is required before the sound of this bird ceases to be a rarity in our woods.

Prof.dr hab. Maciej LUNIAK
Zoology Museum and Institute Polish Academy of Science

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