Territorial behaviour and food composition of two pairs of the little owl Athene noctua Scopoli, 1769, nesting at a distance of only 40 m apart

The little owl Athene noctua (Scopoli, 1769) is a small, nocturnal predator, most active from dusk to dawn, with a two-hour break after midnight. There is little or no hunting during daytime, not even when the birds are raising young (Cramp, 1985). Contrary to these observations, the histology of the retina of the little owl was found to be quite similar to that of diurnal birds, and its colour vision has been reported to be as good as the song thrush’s ( Turdus philomelos; Voous, 1988), suggesting that the little owl may be more diurnal than usually expected. The main food of the little owl comprises small mammals and birds, reptiles, amphibians, insects and earthworms (Cramp, 1985), although several authors have found different proportions in lists of prey. In the Moldavian SSR, the former DDR, France and Spain the number of invertebrate prey exceeded 50%, and in the last two cases was found to equal about 95% (Mikkola, 1983). Contrary to this, during two years of collecting pellets in Poland, Romanowski (1988) found 75% of vertebrate prey (mainly voles, Microtus sp.) and only 25% invertebrates. However, when comparing the number of prey in situations in which both vertebrates and invertebrates are taken, it is important to bear in mind that vertebrate and invertebrate prey deliver very different amounts of food in terms of biomass (e.g. vole versus beetle). Sometimes vertebrate prey, particularly voles and mice, forms a substantial part of the little owl’s food (Voous, 1988), even if this is not well shown by the numbers of this prey. Despite this, one thing is clear – that the proportion of invertebrate prey increases gradually from central Europe to the Mediterranean countries (Mikkola, 1983).