Influence of perch height and vegetation structure on the foraging behaviour of Little Owls Athene noctua: How to achieve the same success in two distinct habitats

Abstract

We compared the diurnal hunting behaviour of a mainly perch-hunting species, the Little Owl Athene noctua, in two structurally different habitats: a treeless pseudo-steppe and a Holm Oak Ouercus ilex rotundifolia woodland in Portugal. While the overall prey availability was similar, perch and vegetation characteristics differed between habitats. Using focal sampling in 29 territories, we measured the type and height of utilized perches, time spent on perches and attack and giving-up distances involved in insect hunting. Moreover, we analysed the interrelationships between behaviour and habitat-specific vegetation characteristics. Little Owls adapted their hunting strategies to habitat features, achieving similar prey detection rates and the same hunting success in the two habitats. In the pseudo-steppe, where only low stone piles were available as perches, owls selected the highest spots (average 0.77 m). In this area, a positive correlation was found between perch height and distance to prey attacked, indicating that perching higher resulted in increased prey detectability. In the woodland, owls selected perches that were lower than maximally available (averages 2.67 m vs. 4.99 m, respectively). Attack distance did not differ between habitats, despite the use of higher perches in the woodland. These results indicate that the more developed ground vegetation in the woodland possibly hampered detection of prey, counterbalancing the possible advantages for prey detection due to the use of higher perches. In such situations, Little Owls seemed to select an intermediate foraging height to maximize prey detectability.