Monitoring of Long-eared Owl

The Long-eared Owl is among the most graceful and slender Bulgarian owls. It has a body length of 31-37 cm (1.1 ft.), a wingspan of 86-98 cm (3 ft.) and weighs between 250 and 330 grams. The owl has typical ‘ears’ from feathers which can reach a length of about 5 – 6 cm. Its prevailing colour is brown-buff.


During the breeding season the Long-eared Owl has been recorded all across Bulgaria to an altitude of appr. 1900 metres (6200 ft.) above sea level. During autumn and winter it forms large flocks of 20 – 40 individuals; such a social instinct and tolerance between individuals distinguishes it from the other species of owl in Bulgaria. The colder the winter, the bigger these roosting flocks are. In winter the Long-eared Owl grows quite bold; the flocks often spend the day on trees in large cities (Plovdiv, for example). About half an hour to an hour after sunset the birds leave their day-time roost and in 10 – 15 min they fly off in different directions. They come back to the trees in the morning, before sunrise.


The Long-eared Owl is considered beneficial as it feeds mostly on rodents; as such it has been protected under the national Biodiversity Act; it is also included in Appendix III of the Bern Convention.

The monitoring of the roost of the Long-eared Owl in the city of Plovdiv – the largest documented winter concentration of the species in the country – is carried out every year since 2006. The survey is carried out once a week between November and March depending on the time of arrival of the first individuals and the departure of the last birds. In colder winters the first owls can congregate as early as October. The objective of the monitoring is to establish the numbers of the species and the dynamics of this particular roost. Besides the number of the roosting owls, the species of the tree they choose is also noted down, as well as the altitude at which they perch. Thus the data reveals more about the habitat preferences of the species too. Meteorological data is also gathered in order to establish its correlation with the numbers of the owl. In order to establish the diet of the species, pellets are collected from the ground under the roost – the remains of the feeding activity of the species. The data is noted down in standard forms which are then integrated in an ornithological data base.