Weather-Dependent Variation in the Winter Diet of Urban Roosting Long-Eared Owls Asio Otus in Pécs (Hungary)

Abstract

Long-eared Owls (Asio otus) usually winter in groups in settlements, hunt at night and rest in evergreen trees during the day. From prey remnants regurgitated as pellets, one can detect species present in their hunting areas and changes in their abundance. Our aim was to reveal how the ratio of small mammal species in Long-eared Owl prey changes during the winter, since weather can influence hunting success and the availability of prey. There were 40–60 Long-eared Owls wintering in the city of Pécs. From November 2014 to mid-March 2015 we collected 6,328 pellets from which 9,087 prey remains were identified. 97.5% of prey consisted of small mammals belonging to 21 species. The diversity of small mammals in the pellets collected in November was significantly lower in comparison with other months. With the increase of precipitation, the relative abundance of the Common Vole (Microtus arvalis) and Common Dormouse (Muscardinus avellanarius) decreased, while that of the Striped Field Mouse (Apodemus agrarius) and Wood Mouse (A. sylvaticus) increased. In the periods when the area was covered by snow, the ratio of the Common Vole as prey continually decreased, probably because it stayed under the snow. Since the availability of the Common Vole declined, the proportions of the Striped Field Mouse and Lesser White-toothed Shrew (Crocidura suaveolens) as alternative prey grew significantly. In low temperature periods, Brown Rats (Rattus norvegicus) and birds are more often preyed upon. Despite the hunting area being predominantly urban, species preferring open grassland habitats were significantly more common. As winter progressed, the role of forest-dwelling species in the diet continuously increased.

Precipitation and prey abundance influence food habits of an invasive carnivore

“…Understanding how predation patterns are linked to weather will be integral to conservation success as climate change continues. Climate can affect both prey availability and nutritional requirements (Konecny, ; Drost & Fellers, ; Cypher et al ., ; Szép et al ., ), resulting in novel predation patterns and new threats for prey species. Cats consumed significantly more lizards in years following dry bio‐years than normal bio‐years.…”

“…Understanding the factors influencing the diet of invasive predators is integral for conserving sensitive prey species. Predation patterns can be influenced by prey abundance (Floeter & Temming, ; Jaworski et al ., ), accessibility (Kelly, ; Grant et al ., ), defense mechanisms (Foltan, ; Murphy et al ., ; Clements, Tambling & Kerley, ; Tallian et al ., ), season (Zielinski et al ., ; Bonnaud et al ., ; Thinley et al ., ; Slauson & Zielinski, ), and weather (Konecny, ; Szép, Bocz & Purger, ). By assessing how these factors influence predation, managers can predict what species may be most sensitive to invasive predators, identify times where species of concern are particularly disposed to predation, and develop management strategies to mitigate threats.…”

Long-eared owls roosted in the forest, still hunted in open land

“…Similarly, during the nonbreeding season long eared owls´ winter roosts have regularly been recorded within human settlements (Škorpíková et al 2005, Noga 2007, Zaňát et al 2007, Ružič et al 2010, where the proportion of synanthropic species in their diet increases with the rising level of urbanisation, but the common vole still represents these owls' main prey (Riegert et al 2009, Sharikov & Makarova 2014, Mori & Bertolino 2015, Szép et al 2018. However, several studies deal with winter roosts located in rural zones such as windbreaks and bushes within agricultural land or forest edges (Czarnecki 1956, EnriquezRocha et al 1993, Smith & Devine 1993, Škorpíková et al 2005, Zaňát et al 2007 and some of them also deal with diet composition (Holt & Childs 1991, Cecere et al 2013.…”

Climate change and perishable food hoards of an avian predator: Is the freezer still working?

“…Harsh wintering conditions and colder weather and precipitation may impair everyday hunting and likely lead to an increase in the use of the hoarded food, especially for inexperienced yearlings. As explained for the increase in the consumption in autumn, also through the winter small mammals may be less available due to the deeper average snow cover (Sonerud, 1986; Szép et al., 2018). A high number of freeze–thaw events indicates a mild winter; a larger number of owl individuals might be able to overwinter and survive in the study area in such conditions and also the hoarded food items might be actually easier to eat because they are not completely frozen.…”

“…Also during winter, a deep snow cover for both age classes of owls were associated with a high proportion of hoarded prey items being consumed by pygmy owls. A long period with a deep snow cover can reduce availability of small mammals to hunting pygmy owls (Korpimäki, 1986; Sonerud, 1986; Szép, Bocz, & Purger, 2018), therefore leading to the consumption of hoarded food. This result is consistent with earlier studies on the accumulation and consumption of prey items in relation to the date of permanent snow cover (Halonen et al., 2007).…”