The winter diet of the rare Tyto alba in contrast to Asio otus on Crimea Peninsula

Abstract

The range of Tyto alba overlaps with that of Asio otus in a large part of the Holarctic. Both species are adapted to open-area hunting and prey upon similar species. In contrast to A. otus, data about the diet of T. alba on Crimea and surroundings are extremely scarce. Our study aimed to describe the prey spectrum of T. alba and evaluate at what extant its diet overlaps to that of A. otus. We evaluated diets based on 48 pellets of T. alba and 88 of A. otus collected from January to March 2018 in the Western part of the Crimea Peninsula. Simultaneously, we assessed the availability of small mammal prey by installing 150 spring-loaded bar mousetraps around the collection sites. Small mammals were the main prey in the diet of T. alba and A. otus (99.2% and 100% of all individuals in pellets). The most consumed species of both species was Microtus socialis (52.3% and 74.4% of all individuals). The second most consumed species of T. alba was Crocidura leucodon, an endangered species in Crimea. The diet of T. alba was more diverse than that of A. otus (Shannon diversity Index: 1.1 and 0.76, Simpson Index: 0.51 and 0.31, respectively). However, their diets overlapped widely (Pianka's index = 0.94). The frequency of mammalian prey in traps correlated moderately with that in A. otus pellets (rs = 0.5, p < 0.2), and it deviated from the frequency of mammalian prey in T. alba pellets (rs = -0.05, p < 0.9). The presence of the endangered C. leucodon in the diet of T. alba reinforce the utility of this predator species as a tool to detect threatened or rare small mammals that are not caught by traps and to increase information about their geographical distribution.

Keywords

• aves
• bicoloured shrew
• diet diversity
• dietary overlap
• social vole
• strigiformes