MANEN W VAN (1992) Selection of territory and nest by Long-eared Owls Asio otus. LIMOSA 65 (1): 1-6.

east of the city of Assen (53.00'N, 6.34'E) since October 1986. The study area includes woodland (208 hal, heaths (217 hal, farmland (798 hal and urban areas (277 hal (fig. 1). Breeding density increased from 0.5 territories/ 100 ha (N=13) in 1986 to 1.6 territories/ 100 ha (N=41) in 1990 (fig. 3), with a maximum density of eight territories in a plot of mixed forest (27 hal. Average nearest neighbour distances in 1987-90 were 589, 571, 472 and 376 m respectively (fig. 2), with minimum distances of 150, 80, 175 and 120 m respectively. Breeding in mixed forest - comprising 77% of all woodland - is preferred (92% of all territories, N=91) (fig. 4). This preference was not related to the supply of old nests, because no differences in nest supply were found between the various forest types. The density of Long-eared Owls in woodlots of various sizes was related to the availability of old nests (fig. 5), with highest densities in very small woodlots ?1 hal. The distribution and abundance of common voles Microtus arvalis, the main prey species in the study area (75% of all prey items, N=30 433), did not affect nest spacing of Long-eared Owls. Interspecific competition with Kestrels Falco tinnunculus for nest sites was almost non-existent, the distribution of Long-eared Owls and Kestrels being complementary in the study area (fig. 8). Interspecific aggression over a nest site was noted only once. Apparently, the distribution of woodland and the location of winter roosts were decisive in spacing of territories during the breeding season. Most pairs settled in the vicinity of winter roosts. With increasing breeding density, the average distance between winter roost and breeding territory also increased (fig. 6), suggesting some sort of spacing despite the observed lack of territorial behaviour. Nests in coniferous trees were preferred as nesting sites, particularly those in firs and spruce (table 1). Cover apparently was very important. Most nests occupied by Long-eared Owls were built by Magpies Pica pica and Carrion Crows Corvus carone (table 2) and ranged in height from 5-16 m (fig. 7). Long-eared Owl Asio otus

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