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  • Author: Ján Obuch x
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Spatial and temporal diversity of the diet of the tawny owl (Strix aluco)

The author compared diet of eight owl species in Slovakia, out of which four species prey in the non-forest environment (Bubo bubo, Tyto alba, Asio otus and Athene noctua), while the other four species prey mostly in the forest (Glaucidium passerinum, Aegolius funereus, Strix uralensis and Strix aluco). Tawny owl (Strix aluco) has shown the highest degree of adaptability when it comes to various types of environment and broad diversity of prey. Appendix 1 presents material of total 225,441 pieces of diet, which contains 69 species of mammals and at least 147 species of birds. While B. bubo diet is typical especially for high presence of bigger prey species within mammals and birds (66 diagnostic taxa), diet of S. aluco is characterized by as many as 89 taxa with higher share than the average of all eight compared owls (taxa with values 1+ and 2+ in blocks as marked by full line). Based on the analysis of 68,070 pieces of S. aluco diet collected in Slovakia, it is possible to differentiate seven basic diet types: A - from lower mountains, B - from middle montane locations, C - from colder and more humid parts of mountains, D - characterized by high share of bats (Chiroptera), E - characterized by high share of slugs (Limacidae), F - from floodplain forests, and finally G - from environment strongly influenced by humans. Diagnostic species for one or several diet types are characterized by markedly higher share than Slovak average. By the large amount of analyzed samples of S. aluco diet it is possible to gain the knowledge about structure of several animal groups from relatively little disrupted forest ecosystems and those from environment to some degree influenced by humans. Diet types represent simplified models, which are understood in a different sense than plant communities. Individual disposition for specific food preference (e. g. Chiroptera) also plays an important role by some tawny owl's specimens. Some types of prey can be further divided into undertypes (e. g. undertypes G1 and G2 in Table 1). Diet of S. aluco has been examined more in detail and over a longer period of time especially in following national parks: Slovenský kras, Muránska planina and Veľká Fatra Mts. Samples from other parts of Slovakia are also presented here according to their relevance to particular diet types. Pellets of S. aluco were collected over a longer period of time (up to 30 years) in several sites and it is chronological periodicity in presentence of diagnostic species, which stands in focus. Long-term changes in S. aluco diet during Holocene were examined in two parts of Veľká Fatra Mts, which are influenced by climatic changes as well as human activity (deforestation and pasture). The author has occasionally collected pellets of S. aluco in several mountains of Europe between Western Alps and Caucasus and from northern border in S. aluco areal, from Trondheim area in Norway. Furthermore, the author presents hereby his own material from pellets of S. aluco from the Middle East to Himalaya (in particular countries of Jordan, Israel, Lebanon, Syria, Turkey, Iran, Kyrgyzstan and Nepal).

Contribution to the knowledge on the synanthropization and dietary specialization of the Ural Owl (Strix uralensis) in urban environment of Košice city (East Slovakia)

S. uralensis is a typical silvatic species, specialized for this life style through its biology and diet. Synanthropization is a rare phenomenon in this species, reflected in the changes of diet and hunting strategies, adapting to the characteristics of the urban environment. Between November 22, 1993 and June 2, 1994, an individual of the Ural Owl was observed 39 times in the urban areas of Košice city. The examination of the pellets revealed that the Ural Owl specialized in hunting Streptopelia decaocto (76.7%) and Columba livia f. domestica (13.4%). These results were confirmed by observations of S. uralensis hunting S. decaocto. This discovery is the first direct evidence of S. uralensis diet adaptation to S. decaocto and feral C. livia f. domestica in Slovakia.

Feeding ecology of a nesting population of the Common Buzzard (Buteo buteo) in the Upper Nitra Region, Central Slovakia

During routine checks of the nests of the Common Buzzard in the Upper Nitra region (Central Slovakia) we collected food remains and recorded all prey given to the nestlings. We present results from the period 2006-2008. 606 food items were determined, comprising mainly mammals (67%). Birds were also frequent (17%), less so amphibians and reptiles (7%) and invertebrates (10%). During the rodent population peak in 2007, Buzzard pairs nesting in the valley preyed mainly on Microtus arvalis, whereas pairs living at the rim of the valley fed on Myodes glareolus and Talpa europaea, and higher in the Vtáčnik Mts birds fed on Apodemus flavicollis. After a massive decline in the rodent population in the following year 2008, the survival rate of the nestlings was very low and the proportion of invertebrates in their diet increased. Birds that were most frequently preyed upon included juvenile Turdus philomelos and Garrulus glandarius, prey identified from amphibian was mainly Bufo bufo, and from reptile prey was largely Anguis fragilis.

Food of the Barn Owl (Tyto alba) in the Eastern Mediterranean

The composition of the Barn Owl (Tyto alba) diet analysed from pellets collected in several regions of the Eastern Mediterranean is presented. In total, 27 samples from 21 sites in S Italy, S Greece (incl. Crete), S Turkey, NW Syria, SW Lebanon, N Israel, and N Egypt were composed of 8842 prey individuals. Mammals represented the dominant part of the prey (90% of the identified prey individuals, comprising 44 species). Birds were less abundant (7%), however, their diversity was enormous (64 species). Amphibians and reptiles were rarely represented in the diet (0.9%), while invertebrates we found more often (2.2%). The relative abundance of particular prey items in the Barn Owl diet was analysed in four geographical regions: (a) SE Europe (Calabria, Peloponnese, Crete), (b) Levantine parts of Turkey and Syria, (c) Lebanon and N Israel, and (d) N Egypt. In complex evaluation of the sample set, endemic forms composed a special group of prey items: Microtus savii, Sorex samniticus, and Talpa romana in Calabria; Microtus thomasi in Peloponnese; Acomys minous in Crete; and Gerbillus amoenus in Egypt. Another group of prey is represented by typical Levantine species: Microtus guentheri, Meriones tristrami, Apodemus mystacinus, and Rana ridibunda. Apodemus flavicollis and Crocidura leucodon were more abundant in Calabria while less abundant in the Levant. Synanthropic mammals (Mus spp., Rattus rattus, Suncus etruscus, Crocidura suaveolens) and birds (Passer domesticus) represented a significant part of the diet in the majority of the studied area.

The Eurasian eagle-owl (Bubo bubo) diet in the Orava Region (N Slovakia)

Food remains of the Eurasian eagle-owl (Bubo bubo) were studied in samples collected from 26 nests. The samples were collected during spring thus represent the prey brought to the nest whilst rearing of chicks. In total 15,196 items of prey were determined. The dominant food items were two smaller species of rodents, Microtus arvalis (39.0%), Arvicola amphibius (12.1%), and the common frog (Rana temporaria; 27.9%). Other prey recorded had low dominance, however, represented a wide range of species. 43 species of mammals and over 80 species of birds were determined. The Orava Region is climatically one of the coldest regions in Slovakia. The abundance of food for nestlings depends mostly on gradational cycles of small species of rodents and on frogs as the alternative food components. The proportion of bigger species of prey is low: from mammals it was mainly Rattus norvegicus (2.3%), Erinaceus roumanicus (0.7%) and Lepus europaeus (0.5%), from birds Corvus cornix (1.1%), Perdix perdix (0.6%) and Asio otus (0.4%). The food supply creating suitable condition for reproduction of Eurasian eagle-owls in the Orava Region has been deteriorating over the last 20 years due to a decrease in agricultural production leading to diminution of non-forest areas.


Between 2005 and 2015 I undertook eight trips to Jordan during which I collected pellets from seven owl species. In them 14,203 food items were identified. Mammals (Mammalia, 46 species, 37.9% of prey items) formed the most numerous component, invertebrates (Evertebrata) made up 33.4%, birds (Aves, 25.4%) were represented with at least 104 species, reptiles (Reptilia) came to 3.2%, and two species of amphibian were identified (Amphibia, 0.2%). Pharoah eagle owls (Bubo ascalaphus) and Byzantine eagle owls (Bubo bubo interpositus) primarily hunt larger mammals and birds, although Agamidae and Scorpiones were also represented more frequently among B. ascalaphus. Mammals predominated among tawny owls (Strix aluco wilkonskii) (Mammalia, 58.9%), mainly the eastern rock mouse (Apodemus mystacinus) (24.9%). For wintering long-eared owls Asio otus otus the most important food was small birds (Aves, 78.3%), especially house sparrows (Passer domesticus), Fringillidae and Sylviidae. For barn owls (Tyto alba erlangeri) the principal prey was small mammals (83.1%), mainly mice (Mus sp.), Günther’s vole (Microtus guentheri), grey hamster (Cricetulus migratorius) and shrews (Soricidae). Hume’s tawny owl (Strix butleri) pellets contained mostly invertebrates (58.9%) and lizards, and their most frequent mammal prey were Wagner’s gerbil (Gerbillus dasyurus) and spiny mice (Acomys sp.). There was an even higher propostion of invertebrates (86.4%) among lilith owlets (Athene lilith). In addition to the insect orders Coleoptera, Orthoptera and Hymenoptera, remains of Scorpiones and Solifugae were also frequently found. The summarized results from individual owl species are compared with those gathered by the author in the surrounding Middle Eastern countries: Israel, Syria, Lebanon and Egypt.


We completed data on the diet of the barn owl (Tyto alba) predominately from pellets for the period of the last 50 years from Slovakia. We analyzed material from 251 locations and 16 territorial units. The aggregate represents 119,231 pieces of prey from 47 species of mammals (Mammalia, 95.7%) and 58 species of birds (Aves, 3.9%), with a small representation of amphibians, reptiles (Amphibia and Reptilia, 0.2%) and invertebrates (Invertebrata, 0.2%). The obtaining of food among the owls is limited to synanthropic environments and the surrounding agricultural landscape, and the centre of its distribution in the recent period (i.e. the past 50 years: 1965-201 5) has been concentrated mainly on the southern parts of Slovakia. In this environment the common vole (Microtus arvalis, 59.6%) is the primary prey. Additional prey are rodents of the family Muridae: Mus musculus (5.6%), Micromys minutus (2.2%), Apodemus microps (2.2%), A. flavicollis (2.0%), A. sylvaticus (1 .6%) and A. agrarius (1 .5%); insectivores of the family Soricidae: Sorex araneus (6.2%), S. minutus (2.4%), Crocidura leucodon (4.8%) and C. suaveolens (2.8%); and the house sparrow Passer domesticus (2.9%). In the higher situated Turcianska kotlina Basin the species M. arvalis (74.3%) has higher domination, and instead of the white-toothed shrews the water shrews Neomys anomalus (2.8%) and N. fodiens (1 .3%) are more abundantly represented. In 3 localities owls focused on hunting bats; for example, in the church in Ratková the order Chiroptera made up 35.2% of prey. From the subrecent period (i.e. from before more than 50 years ago) we evaluate 4 samples from the territory of Slovakia with 15,601 pieces of prey ofT. alba. Before more than 50 years ago owls were also more abundantly represented at higher elevations in Slovakia, evidence of which is Weisz’s collection of pellets from 1 6 localities in the Ondavská vrchovina Upland in the years 1945 to 1963, but also a registry of data from the 19th and 20th centuries from higher located basins. In 4 samples of food from the subrecent period diversity in the representation of owl prey is higher, accompanied by low domination ofM. arvalis and a more abundant representation of murids from the genera Mus and Apodemus. The oldest sample, dated to the 16th century, is from a church in Žilina-Rudiny


Between 2008 and 2015 we collected pellets of the Eurasian eagle-owl (Bubo bubo) in the Trøndelag region of central Norway and identified the food remains in these samples. We collected material at 45 sites with samples from a total of 76 nests. Some of the samples were from older and already abandoned nests, but at several sites we also found and collected fresh B. bubo pellets. In total 40,766 items of prey were identified from the osteological material. The most dominant food components were mammals (Mammalia, 25 species, 63.5%). The species representation of birds was very diverse (Aves, more than 150 species, 19.4%). Of amphibians (Amphibia, 1 6.8%), the well-represented species were Rana temporaria. Fish (Pisces, 0.3%) were represented rarely, while invertebrates were represented only sporadically (Invertebrata, 0.05%). A special composition was found in the diet spectra of the mammals and birds in the mountainous areas at altitudes between 220-780 m above sea level. The highest proportion of frogs was found in areas in the proximity of the mainland shore. On the northern islands located near the coast a significant proportion of the B. bubo diet consisted of rodents (Rodentia). On the more isolated southern islands of Frøya, Hitra and Storfosna the main prey was sea birds, and of the mammals there were also hedgehogs and rats.


Long-eared owls’ winter roosts located within forest, compared to their winter roosts in human settlements, often escape human attention. Only minimum information has been published about winter roosts located deep in the forest. During the years 2005 to 2016, we collected long-eared owl pellets at irregularly occupied forest winter roosts. Compared to the diet at winter roosts in human settlements, the long-eared owls roosting in the forest surprisingly significantly more frequently hunted the common vole. Moreover, we did not record higher consumption of forest mammal species in the diet of owls at forest winter roosts. Long-eared owls roosting in human settlements hunted significantly more birds. The results show that, despite the location of deep forest winter roosts, long-eared owls preferred hunting the common vole, i.e. hunting in open agricultural land. The study also points out the lack of knowledge about winter roosts located deep in the forest.


Data on the food of the Eurasian pygmy owl in Slovakia was collected in 1999−2014 at 12 breeding locations in 7 mountain ranges of the Western Carpathian Mts and 1 range belonging to the Eastern Carpathian Mts. The basis of the evaluation of the food spectrum of prey of G. passerinum was the collection of pellets, osteological remnants and feathers from birds beneath nest cavities and roosting places of females in the months of May to July, that is, in the period of feeding young in the nest. Overall samples of food from 12 nests at elevations of 650−1,260 m a.s.l. were collected; from the largest of the three nests in the upper Nitra Region, from one nest in the Západné Tatry Mts and from three nests in the Volovské vrchy Mts. We compared these data with existing published data from Slovakia. A higher share of birds (65.0%) was found in the obtained material than mammals (34.8%). In the samples from 12 locations 10 species of mammals and 33 species of birds were found among the 377 individual prey samples. Among mammals, forest species of rodents predominated: Clethrionomys glareolus (22.8%) and Apodemus flavicollis (6.6%). The species Microtus arvalis (2.7%) was less abundant than in the stores of food from the Chocské vrchy Mts (35.4%). From the broad spectrum of songbirds, no species exceeded a presence of 7%. Species from the families Sylviidae, Turdidae, Paridae and Fringillidae were more numerous, while the species Phoenicurus phoenicurus, Motacilla alba, Carduelis cannabina, Dendrocopos minor and Passer domesticus were among the more uncommon prey. In total 582 individual prey were determined from the food remnants of G. passerinum in Slovakia (present study and other published studies). The species Clethrionomys glareolus occurred with a higher dominance than average in the pellets of G. passerinum in the mountains which border the region of the upper Nitra. In the Belianské Tatry Mts the most abundant rodent species was Terricola subterraneus, while in the mountains of eastern Slovakia the yellow-necked mouse Apodemus flavicollis was most often hunted, and of the songbirds, the coal tit Periparus ater. Among songbirds hunted near the breeding grounds of G. passerinum in the Považský Inovec Mts the collared flycatcher Ficedula albicollis was the most numerous. Among the most numerous songbirds which are evenly represented in all compared areas were: Regulus sp., Certhia familiaris, Poecile montanus and Cyanistes caeruleus.