Ardelean, Gavril (szerk.): Satu Mare. Studii şi comunicări. Seria ştiinţele naturale 6. (2005)

Researches ont he prey selection of barn owl (tyto alba) in Statu Mare county

Satu Mare - Studii și Comunicări Științele Naturale — Voi. VI (2005) RESEARCHES ON THE PREY SELECTION OF BARN OWL (TYTO ALBA) IN SATU MARE COUNTY SÍKÉ TAMÁS', SZODORA Y-PARÁD1 ABIGÉL2 1 - Muzeul Județean Satu Mare, 440031 Satu Mare, V Tucadu 21, 2 -Asodația pentru Protecția Uliedlor din România, 440014 Satu Mare Rezumat. Despre gradul de specializare a hrănirii la strigă (Tyto alba), respectiv lista speciilor pe care le preferă există păreri diferite în literatura de specialitate. Importanța problemei constă în faptul că analiza ingluviilor de strigă este una dintre cele mai răspândite metode aplicate în monitoringül mamiferelor mici. In decursul cercetării ne-am încercat să răspundem la întrebarea, dacă strigile au preferințe trofice față de anumiți taxoni, sau componența hrănii este determinată de abundența speciilor de pradă potențiale. Pentru a răspunde la această întrebare am comparat rezultatele analizei ingluviilor cu rezultatele capturărilor efectuate în revirul strigilor. Capcanele au fost amplasate în locuri în aporpierea cărora au fost observate vânând strigi din două localități învecinate. S-au efectuat patru eșantionări cu ajutorul capcanelor, fiecare pe o perioadă de cinci zile Ingluviile au fost adunate din locurile de odihnă din timpul zilei. Rezultatele, neluând în considerare diferențele datorate metodelor diferite de analiză, sunt similare, adică nu există diferențe mari între componența speciilor capturate și acelor aflate în ingluvii. Hrănirea strigilor reflectă densitatea populațională a speciilor pradă disponibile (microtide, muridé, soricide) fără să prezinte preferințe față de anumiți taxoni. Summary. There are different approaches in the literature about the dietary specialisation of the barn owl. The owl pellets analysis is one of the most general applied methods in the monitoring of small mammals. During my researches I tried to find even owls have special food preferences regarding different taxons or the abundance of the potential prey species determinates the component of the food. In order to answer this question there were compared the results of the pellet analysis and the results of the captures made in the hunting area of the barn owl. The traps were placed out in those places where were observed hunting owls from 2 neighbourhood villages. 4 times were the traps taken during 5 days. The pellets were collected from the (roosting site) of the owls in day time. The results are similar (if we do not take into account the differences due to the different methods of analysis) namely there is not a significant difference between the components of captured species and those being in the pellets. The diet of the owls reflects the populational density of the available prey species (voles, mice, shrews) without presenting preferences of the certain taxons. Introduction The most part of the food spectrum of barn owls (Tyto alba) includes small mammals but the number of the consumed species is high (Mikkola 1983). Taking into account the huge number of the prey species and the fact that the component of food is changing in different territories (Bősé & Guidali 2001) we can draw the conclusion that the feeding of the species is not specialised in high level it is determinated by the available prey spectrum. In the literature there are many argues about the level of the food specialisation. There are studies in which strong relation is proved between the available food recourses and the representation of certain species in the diet. (Yom-Tov Wool 1997, Evans & Emlen 1947, Luiselli & Capizzi 1996). In other studies are presented visible differences in this concern (Johnston & Hill (1987): the high feeding preferences concerning birds by owls in small islands, or Bellocq (1998): the preferences of prey items with special body weight. The food prefernece of barn owls obtains a high importance taking into account that pellet analysis is a most general applied method in small mammal monitoring. During our studies we tried to answer the question even barn owls do special prey selection concerning some species or group of species or the component of the food spectrum is determined by the available populational trends of preys. In order to find the answer it were compared the results of the small mammal trapping on the hunting area of the barn owls with the contain of the barn owls pellets. Materials and Methods The breeding place of the owls was identified through nighdy observations. By following the direction of the nighdy flight of the owl had been identified the place where later the owl was observed hunting. The traps were placed out in those areas where hunting owls from two neighboring settlements were observed. This territory is a pasture that takes place between Turulung and Turulung-Vii. The area is covered gradually with bushes in northern -southern direction and ends in a thick bushy on forest edge area with many ox bowls. In western direction of Turulung-Vii can be found agricultural lands which are cropped with divert agricultural produces. The territory is a fresh, spontaneous scrubbing, lowland grass with good water supply which was utilized as pasture, (the usage of the territory as pasture was given up gradually in last 5-10 years). The characteristic species are the following: Festuca pseudovina and F. pratensis, Dactylis glomerata and Poa angustifolia. Pioneer hydrofeel plants are formatted on the deeper surfaces of the pasture covered persistently by water and along some water 112

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