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 (r s = 0.5, p < 0.2), and it deviated from the frequency of mammalian prey in T. alba pellets (r s =-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.

The diversity-area relationship for waterbird communities in small artificial reservoirs over winter

“…The Ehyz-Oba reservoir (near the town of Bakhchisarai) is surrounded by arable fields, artificial forests, roads and settlements; the Partyzanske reservoir (south-west of Simferopol city) lies between a forest and a settlement in the north; the Simferopolske reservoir (south of Simferopol city) is surrounded by settlements to the west and an artificial forest to the east; and the Bilohirs'ke and Taihans'ke reservoirs (east of the town of Bilohirsk) are located side by side among arable fields and settlements. The reservoirs are all between 300 and 400 m above sea level, surrounded by predominantly forested habitats (Kucherenko & Ivanovskaya 2020), with some open grassland areas and arable fields, and all are located close to residential areas and roads. None of the wetlands investigated have aquatic vegetation.…”

“…Over 320 bird species have been recorded in the country (e.g. Kostin 1983, Prokopenko et al 2012, Kucherenko et al 2017b), and millions use the peninsula as migration and overwintering stopovers, many of which are of global and local importance (Kostin 1983, Akimov & Radchenko 2009, Ivanov et al 2015, Andruyshchenko et al 2019, Kucherenko et al 2020). Most of these sites are concentrated in Natural Reserves, 12 important bird areas (Dudkin 2003) and six Ramsar wetlands (Ramsar sites information services 2022, https://www.ramsar.org/wetland/ukraine).…”

“…For example, Eastern Syvash, the nearest important hotspot for birds, especially in winter, is located more than 100 km from the reservoirs, while the closest distance to the sea coast from the reservoirs is from 30 to 50 km. Many studies have examined bird diversity and ecology along the Ukrainian Azov-Black Sea coast and Crimea (Andruyshchenko et al 2015, 2019, Kucherenko & Kalinovsky 2018, Kucherenko et al 2020). These have highlighted the significance of wetlands for different species in terms of phenology, dynamics and distribution (e.g.…”

“…Kucherenko & Chirniy 2011, Kucherenko et al 2015, 2017a). Immigration, one of the processes in the island biogeography equation, is well documented in Crimean avifauna (Prokopenko et al 2012, Tsvelykh & Kucherenko 2020), including aquatic species (Vergeles et al 2012, Kucherenko et al 2015, 2017b, 2018); however, such studies tend to concentrate on nesting species. Nevertheless, all phenological periods are important for monitoring bird activity, and data from all seasons are required to fully assess the significance of a locality for bird maintenance during winter (Kwieciński et al 2016, Morelli et al 2018).…”