Cantonnement et comportement vocal du grand-duc d'Europe Bubo bubo dans les monts de la Sierra Morena (Sud de l'Espagne)

Between 1981 and 1987 a 925 km 2 area of the Sierra Morena in southern Spain held, on average, one pair of Eagle Owls Bubo bubo per 57.8 km 2 (1.73 pairs/100 km 2 ). The mean home range size was 8.59 km 2 and mean radius of activity 2350 m. For convenience the nest was considered to be at the centre of the home range, although the shape of the home range depends on the physical and structural features of the environment as well as availability of favourable hunting, breeding and nesting sites. Altitude within the area surveyed ranged between 380 and 1300 m ; the Eagle Owl prefers mid-altitude mountain habitats, mean altitude was 600 m., no nest sites were found above 700 m. All nests of a given pair were located within a small area in the home range. Both perch-to-perch and perchto-nest distances are directly correlated to territory size ; perches farthest from the nest are used for hunting and calling, while those nearest are used for nest teritory surveillance. Distances between successive perches show the Eagle Owl to be highly mobile within its home range. Calling occurs from autumn until the middle of the breeding season, being most frequent between early January and mid-February. Adverse weather (wind or rain) reduce frequency and interferes with the territorial function of calling.