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  24.03.2021, 13:06h

Monitoring nesting pairs od Eurasian eagle owl (Bubo bubo)

The aim is to establish a permanent monitoring programme to monitor the population trends of the Eurasian eagle owl in Croatia, its distribution, and the causes of threat.

The data collected will allow for better planning and protection of this strictly protected species.

The Public Institute of Krka National Park has joined in a national programme to monitor nesting pairs of Eurasian eagle owl (Bubo bubo) in the park area. Monitoring was organised by the BIOM Society, and was conducted from 1 February to 10 March. We would like to thank the members of the BIOM Society for coordinating the monitoring programmes, and for their training and advice.

Park staff visited 17 locations along the Krka River canyon, listening for the songs of males in the early evening hours just after sunset.

The results of this year’s monitoring session were exceptionally encouraging. In all, 11 singing males were recorded from the upper course, through the middle reaches, to the lower course of the river. We confirmed earlier assessments of ten nesting pairs of Eurasian eagle owl in the park, and for the first time, a male’s song was held in the canyon upstream of Bilušića Buk. Only one active nest with a female incubating her eggs was visually confirmed, in a crack of a steep cliff. This nest will continue to be regularly monitored, and all changes tracked. The Eurasian eagle owl is a protected species, and a target species in the ecological network location HR1000026 Krka and surrounding plateau. The aim is to conserve this population and habitat to support the nesting of a population of 50 to 70 pairs.

The Eurasian eagle owl is Europe’s largest owl, up to 70 in length with a wingspan of 170 cm. In addition to its size, it is also easily recognisable for its large ear “tufts” and large reddish-orange eyes. Its flight is powerful due to the wide, rounded wings. Like all owls, the legs are fully feathered with strong talons used to catch prey. The sexes do not differ in appearance, except for size, as the female is much larger than the male. The diet usually consists of hares, rodents and wetland birds, and it needs open habitats to hunt. It does not build a nest, instead it uses hollows and cracks in rocks, the nests of other bird species, hollows under tree roots, and hollows in tree trunks. Pairs are monogamous and remain together for life, and once they establish a territory, they remain there. It is interesting that the males have virtually no contact with the chicks, he hunts and brings the female food, and she feeds them. The female alone incubates the eggs, and protects the chicks from inclement weather and prey until they are two to four weeks old. At this age, the chicks leave the nest and are capable of taking shelter when in danger.

In Croatia, the Eurasian eagle owl is threatened directly by electrocution on power lines, poaching, intentional or unintentional poisoning, and collisions with wind turbine blades. Indirectly, this species is threatened by habitat conversion, due to intensified agriculture and abandoning traditional animal husbandry, which results in habitat succession. It is also threatened by disturbances to nests due to recreational activities. The overall population of the Eurasian eagle owl in Croatia is assessed at 800 to 1200 pairs.