1 Department of Wildlife Ecology and Biodiversity, National Environmental Research Institute, Aarhus University, Aarhus University2 Department of Bioscience - Wildlife Ecology, Department of Bioscience, Science and Technology, Aarhus University3 unknown4 Department of Bioscience - Wildlife Ecology, Department of Bioscience, Science and Technology, Aarhus University
Behavioural choices made by individuals about where to forage can identify important habitat parameters at a given stage of the year. In Denmark, little owls have disappeared from most of their former range and are steadily decreasing in numbers, possibly because of changed land use practise in the agricultural areas where they live. To identify vital landscape variables for foraging of the remaining population, we analysed habitat use of 29 radio-tagged little owls (14 pairs, 1503 telemetry fixes) tracked at night over a two-year period. The proportion of time (i.e. telemetry fixes) spent in different habitat types (analysed with GLMMs, treating territory ID as random factor) of different habitat types (categorised as ¡§cultivated fields¡¨, ¡§gardens and built-up areas¡¨, ¡§grazed land¡¨, ¡§continuous tree vegetation¡¨ and ¡§uncultivated open areas¡¨) was similar for males and females, but varied seasonally and as function of temperature and distance to the nest. From September through May little owls spent 60% of their time on cultivated fields (covering 67% of the area within 1 km radius of nests) as opposed to 32% in June-August (¡¥summer¡¦) when grown crops covered most fields. Gardens were highly preferred with a seasonal usage of 44% in summer and 18% in the rest of the year (as opposed to 3% cover), followed by horse-grazed areas (4% use year-round, 2% availability). Cattle-grazed areas were preferred in summer (10% use, 5% availability) and used in proportion with availability during the rest of the year. At temperatures between 0"aC and 10"aC, more than 75% of all fixes of silent (potentially foraging) owls were located in open habitats, whereas areas with trees and buildings were increasingly used at temperatures below 0"aC or above 10"aC, apparently reflecting temperature dependent hunting tactics. However, relative to availability, hedgerows were generally not preferred over open land. The results show that little owls on an annual basis utilized most available habitats within their range including intensively farmed cropland, but that foraging decisions were conditioned to the prevailing weather conditions at any given night. Access to a wide range of different habitat patches within a reasonable distance from the nesting place, differing in foraging profitability at different time of the year and at different weather regimes might therefore be important to secure reliable food supply. The extensive use of farmland indicates that habitat improvement initiatives for little owls will be difficult without including the foraging potential of these economically exploited areas. Land use policies favouring maintenance of permanently grazed areas within 313 m of nests, where owls spent 75% of their time, might improve the foraging situation during the breeding season in summer when cropland were most underused and grazed areas most preferred.