# Diet and Hunting Range of Wintering Long-Eared Owls (Asio otus) Depend on Land Use

## TL;DR

Long-eared Owls adjust their diet and hunting range based on the amount of built-up land around their roosts, showing how urbanization affects their prey availability.

## Contribution

This study demonstrates that owl pellets can track land-use impacts on small mammal communities and highlight the owls' role in pest control.

## Key findings

- As built-up areas increase, access to main prey like voles decreases, forcing owls to eat a more varied diet.
- Owls in cities show higher prey diversity but lower specialization compared to those in villages.
- Pellet analysis reveals a strong match between prey and habitat in villages, but not in cities.

## Abstract

Long-eared Owls often roost in coniferous trees during winter within human settlements. These owls regurgitate pellets with the remains of their prey. Analysis of the content of these pellets can show what prey is available in the surrounding landscape. We studied whether the amount of built-up land around owl roosts affects the availability of prey for owls. During one winter, we collected large numbers of pellets from a village, a town, and a city in southern Hungary. As built areas increased, open fields and forests decreased, limiting access to the owls’ main prey, especially voles and other small mammals. In more urban places, owls ate a wider variety of prey, but each type made up a smaller share of the diet. The match between prey in the diet and nearby habitats was strongest in the village and weakest in the city. Our results show that owl pellets can help track how land-use changes affect small mammal communities, and they highlight the owl’s valuable role in naturally controlling pest species.

Long-eared Owls (Asio otus) overwinter in groups, mainly on coniferous trees in human settlements. These owls regurgitate the indigestible parts of their prey as pellets. Analysis of pellet contents provides valuable information on diet composition and reflects the characteristics of the hunting area. We assumed that prey availability for owls is influenced by the extent of built-up areas and by the distribution of habitats around the roosting site. In the winter of 2016/2017, we collected three samples of 1000 pellets from settlements in the southern part of Hungary: the village of Udvar, the town of Mohács, and the city of Pécs. Species accumulation curves were calculated based on cumulative prey species richness and rarity. To assess the effect of built-up areas, we compared the diet composition of owls wintering in settlements of different sizes. To estimate the size of the hunting area, we compared the relative abundance of small mammal species with different habitat preferences detected in the pellets with the proportion of habitat type within circles of one, two, and three kilometres around the roosting sites. The proportion of open and forested habitats decreased as the extent of built-up areas increased. This reduced access to the owls’ main prey, especially Common Voles (Microtus arvalis) and other small mammals. As a result, the minimum number of pellets needed for a representative sample was at least 300 in the village, 600 in the town, and 1000 in the city. In the city, owls showed higher prey species richness, greater diversity, higher evenness, and a wider food niche than owls in the town or village. In the village, the relative abundance of small mammal species associated with urban, open, forested, or wetland habitats in the owl diet fully matched the distribution of these habitat types within a three-kilometre radius around the roosting site. In the town, such matching was found only for open and forested habitats. In the city, this relationship was observed only for wetland habitats. Pellet analysis of wintering Long-eared Owls can reveal the impact of land use on small mammal prey communities and highlight important ecosystem services of this owl species, including its role in reducing small mammal pests.