SRJ10262Volume501

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Tab. 16. Comparison of the diet of Strix aluco in some parts of the Sør Trondelag region (Norway)

Tab. 16. Porovnanie potravy Strix aluco v niektorých regiónoch v kraji Sør Trondelag (Nórsko)

diet )aluco Strix( owl tawny of diversity chronological and Spatial J: Obuch

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Tab. 16. continuation / pokračovanie

.8-0057-012-2478/v10262.10 DOI: .120–1 5: 2011, Journal Raptor Slovak (RPS) Slovakia of Protection Raptor ©

Obuch J: Spatial and chronological diversity of tawny owl (Strix aluco) diet

all samples from the same location and same sampling datetogether,weselectedonlythosebodypartsspecified in our methods. The results of species identification of birds or mammals were recorded only after sorting out all bones from the sampling occasion.

For the identification of mammals we used jaw bones, in moles also humerus and in hares the heel bone (calcaneus). The identification of theArvicolidae family also involved careful sorting of detached first lower molars M1, which allow the identification of individual species. In other mammal species (families Soricidae, Muridae, order Chiroptera) we searched for differential characteristics which allow the identification of species even after the teeth have been removed. The presence of reliable comparative skeleton material is crucial for the identification of bone fragments.

According to the handbook by März (1969), we sorted out four types of avian bones and the occurrence of aparticularspeciesinthesamplewasdeterminedfromthe most numerous of these bones. The analyzed material is deposited at the Botanical Gardens of Comenius University in Blatnica for later revision, or closer identification of specimens that were classified to higher taxonomic levels.Thematerialcanlaterbeusedfortaxonomicstudies. Several authors use only beaks for the identification of birds.Bocheńskietal.(1993)studiedwhichbirdbonesare most numerous in the pellets of S. aluco and B. bubo and howfragmentedtheywere.Accordingtoournotesonthe analysis of S. aluco pellets in this study, we can conclude thatbyusingbeaksonly,thenumberofbirdsinthepellets would be underestimated to 25% of the real number. The accuracy of the identification to species level would also belimited.Inourcasetheuseoffourbonetypesprovides complementarymaterialthatisusedtoclearupanydoubtful results caused by bone fragmentation. The checks of food reserves in the nests of the B. bubo revealed that in cases of large prey (e. g. hedgehogs or ducks) the adults feedtheiryoungonlywithfleshybodyparts,andheadsare disposed of in the pellets of the adults outside the nest.

In our smallest owl species G. passerinum, heads are absentinthepelletsnotonlyforpreyofthepasserinebirds (Passeriformes),butalsorodents(Rodentia).Uttendörfer (1939,1952) and other German authors included in prey numbersfromthepelletsalsotheresultsfromtheidentification of feathers found around the pellet sampling spot. In Slovakia, the method of results accummulation from the food reserves in the nest, skeleton remains, feathers and pellet samples is used in the research of the diet of the birds of prey, since most bones in their pellets are digested (e. g. Dravecký et al. 2008).

The method of marked differences from the mean (MDFM) assumes binomial distribution of discrete numbers in a contingency table and is based on χ2 values. It does not test overal similarity of samples within a datasetbutworksoutwhichitems(species)inthedataset show significantly different abundances from the mean (summary) values. The measure of deviation difference is derived from the geometric relationship between the parameters of the basic boundary line: 1, 2 (coefficient) and4(constant).Weanalyzedthesamedatafirstbycalculating a similarity dendrite using the MDFM method and thenbyclusteranalysisproducingadendrogram,andboth methods yielded similar results (Miklisová et al. 2001). However, the MDFM method has identified diagnostic species which define similarities or differences between samples independently of their dominance. The marked differencesfromthemeanmethod(MDFM,Obuch2001) have so far only been used by a few Slovak researchers. Some do not consider this a correct method (Mlíkovský 1998),whileothersusefreestandardcomputerprograms forthestatisticalanalysisoftheirdata.TheZberdatabase program (Šipöcz 2004) is used only by the Botanical Gardens of Comenius University in Blatnica and the headquarters of the Raptor Protection of Slovakia civic associationlocatedinBratislava.Thiscomputerprogram allows the synthesis of a great amount of data. This method has also been applied to some literary data.

Poland. Many research studies about the owl diet including S. aluco have been published. For comparison we selected several studies from the urban environment and larger forest complexes.

The diet of S. aluco in the cities and adjacent areas (Appendix 36). The food samples of S. aluco from large cities in Poland were distinguished by high proportion of birds (Aves, 47.3%):

In Poznan, Cracow and the centre of Warsaw, the dominant prey species included the sparrow species P. domesticusandP.montanus,inTorunalsolargerspecies:

S. decaocto and Sturnus vulgaris.At the Salvator Hill at Cracow two frequent species of trushes (T. merula and T. pilaris). Great part of the birds (10%) were only determinedasPasseriformesorAves.Goszczynskietal.(1993) referred about increasing proportion of birds in the food samples of S. aluco in the suburbs of Warsaw (Puszcza Kampinsoka) and parks at newer residential areas and in the centre of the city.Their data was combined into three groups. In the woodlands in the city suburbs, the forest rodent species were more frequent (A. flavicollis and C. glareolus), in the centre of Warsaw rather the synanthropic species (R. norvegicus and M. musculus), while

thestripedfieldmouse(A.agrarius)wasdominantinthe parks on the city suburbs. We added the data of Wiacek & Niedzwiedz (2008) from three sites located from the suburbs to the centre of Lublin. The distribution of diagnostic species in the sum of these samples most closely resembles the results from the suburbs of Warsaw.

The diet of S. aluco in forested areas (Appendix 37). In contrast to the Slovak landscape, Poland has a much greater territory and most of it is covered with plains or low hills.Three of the six food samples of S. aluco in our comparison came from the north-eastern part of Poland, one from a moderately high mountain range (Beskid Niski Mts.) on the border with Slovakia. In the sample fromLuknajolake,onlymammalswereidentified.Birds (4.3%) generally make up a less important food component of S. aluco and it is hard to estimate their species composition, because house sparrows (P. domesticus) wereidentifiedonlyinthesamplesfromtheBeskidNiski Mts, and thrushes (T. philomelos) from the Romincka forest. Data on other species are scarce. Frogs are quite frequentintwosamplesfromnorth-easternPoland,espe- cially R. temporaria and R. arvalis at the Romincka site. Mammals(Mammalia,80.2%)arepresentmostmarkedly atLuknajolakeasblocknineofmostlymarshlandspecies. Not all species were determined; otherwise the resulting proportion would be lower. The proportion of bats in the dietofS.alucofromtheSzachownicacaveatCracowwas quite significant (Chiroptera, seven species, 21.6%).

Germany. Germany was the cradle of owl pellet research. Uttendörfer (1939,1952) concentrated in his works on contemporary data on the diet of birds of prey and owls not only from Gremany but also from other European countries, and he also mentioned studies from other continents. His works lack more detailed geographical descriptions of the sampling sites. Thus the data from Schaefer from Slovakia were also included. Silesia was then a part of Germany and presently it has become difficulttoidentifytheGermannamesofthesitesinPolish territory.Thisresearcheralsodidnotincludeinformation on who collected and analyzed the samples. In the introductiontohisstudyfrom1939heacknowledgedonlyhis closest colleagues, not mentioning dozens of those who collected samples. Some of his students (e. g. Schaefer 1962, März 1954) later re-published material already presented by Uttendörfer.

Surroundings of Herrnhut, south-eastern Germany (Uttendörfer 1939, 1952) (Appendix 38). The samples were collected over a period of several years at several sites, which are marked beside the local description with the letter H (abbreviation of the town Herrnhut, where

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Tab. 17. Diet of Strix aluco in the Near East region

Tab. 17. Potrava Strix aluco na Blízkom Východe