Slovak Raptor Journal 2013, 7: 37–42. DOI: 10.2478/srj-2013-0007. © Raptor Protection ofSlovakia (RPS) Abundance of raptors and habitat preferences of the common buzzard Buteo buteo and the common kestrel Falco tinnunculus during the non-breeding season in an agricultural landscape (western Slovakia) Abundancia dravcov a využívanie a preferencia biotopov myšiakom lesným Buteo buteo a sokolom myšiarom Falco tinnunculus počas nehniezdnej sezóny v poľnohospodárskej krajine (západné Slovensko) Vladimír NEMČEK Abstract: Habitat use and preferences by raptors were studied during three non-breeding seasons (2011–2013) in an agricultural landscape in western Slovakia. The non-breeding season on agricultural land showed high variation and changes in the cover of habitats related to human activities. The most abundant raptor species were the common buzzard Buteo buteo (L.) (152 indivi- duals) and the common kestrel Falco tinnunculus (L.) (78 individuals). The common buzzard preferred alfalfa and avoided ploughed fields. The common kestrel showed a high habitat preference for alfalfa, corn fields, stubbles and fallow. It also avoided ploughed fields and wheat. Abstrakt: Počas troch mimohniezdnych sezón (2011–2013) bolo skúmané využívanie a preferencia biotopov dravcami v poľ- nohospodárskej krajine na západnom Slovensku. Mimohniezdna sezóna v poľnohospodárskej krajine preukázala vysokú variáciu a zmeny v pokrytí biotopov vo vzťahu k ľudským činnostiam. Najpočetnejším druhom dravcov boli myšiak lesný Buteo buteo (L.) (152 jedincov) a sokol myšiar Falco tinnunculus (L.) (78 jedincov). Myšiak lesný preferoval biotopy s lucernou a vyhýbal sa zoraným poliam. Sokol myšiar preukázal vysokú biotopovú preferenciu pre lucernu, kukuricu, strniská a úhory. Tiež sa vyhýbal zoraným poliam a pšenici. Key words: landscape, agricultural land Vladimír Nemček, Raptor Protection of Slovakia, Kuklovská 5, SK–841 04 Bratislava, [email protected]. Acknowledgments: This study was supported by the international project Conservation of Raptors and Owls – Slovakia – Austria CORO-SKAT according to European Regional Development Fund within the Cross-Border Cooperation Programme Slovakia – Austria 2007–2013. I would like to thank Raptor Protection of Slovakia for the opportunity to work on this project. Introduction 1980). It breeds on trees and cliffs (Sergio et al. 2002). During the non-breeding season raptors often have diffe- This species inhabits a great variety of landscapes but rent habitat and environment requirements than they have mainly mosaics of woodland and agricultural areas during the breeding season. Limitations in this period are (Bijlsma 1997). It is a typical perch-hunting predator. Its food resources and habitats where prey is available main prey consists of small mammals, lagomorphs, (MacArthur & Pianka 1966, Newton 1998). birds, reptiles and worms (Mebs 1964, Graham et al. A number of studies were carried out during the 1995, Kenward et al. 2001, Sergio et al. 2002, Šotnár winter months involving the counting of wintering rap- & Obuch 2009). The population of the common buzzard tors and recognizing their habitat use (Ševčík 1995, in the non-breeding period is formed of birds wintering Wuczynski 2003, Nikolov et al. 2006, Schindler et al. in Central Europe (Northern populations) and of the lo- 2012, Baltag et al. 2013). Habitats in agricultural land cal non-migrating population (Cepák et al. 2008). Du- rapidly change during autumn and winter, because ring winter the species is strongly connected to open fields are ploughed and also cropped. The agricultural habitats (Danko et al. 2002). landscape is composed of important foraging habitats The common kestrel is also a common species in for raptors hunting in open areas. Europe (Village 2010). It nests in trees, on buildings and The common buzzard is the most abundant bird of close to pastures, grasslands, agricultural land and in prey in the Western Palaearctic (Cramp & Simmons built-up areas (O’Connor 1982, Aviles et al. 2001). The 37 Nemček V: Abundance of raptors and habitat preferences of the common buzzard Buteo buteo and the common kestrel Falco tinnunculus during the non-breeding season in an agricultural landscape (western Slovakia) dominant prey of this species is composed of small sunflowers, ploughed fields and stubbles. Beet and rape mammals, insects and birds (Korpimäki 1985, Darolová were merged into a single category because of the very 1989, Van Zyl 1994, Gil-Delgado et al. 1995, Valkama small area of beet. The highest habitat diversity was et al. 1995, Romanowski 1996, Piattella et al. 1999, recorded in September (Shannon index = 1.57). In Sándor 1999, Salvati 2002, Souttou et al. 2006, Noga autumn, the landscape was more diverse due to the hig- & Kečkéšová 2008). her cover of stubbles and fallow. The lowest values were The primary aim of the present study was to recon- recorded during the winter months. Winter habitats were sider the relationships between raptors and agricultural predominantly formed of ploughed fields and wheat. habitats during the non-breeding season. I tested the The size of field parts ranged from 0.3 to 143.6 ha. hypothesis that raptors use habitats in the agricultural landscape in proportion to the habitat coverage. D a t a c o l l e c t i o n The raptor counting was performed during the non- Material and methods breeding season from 2011 to 2013 (twice in November S t u d y a r e a and December of 2011, four times in January, Septem- The study was carried out in an open, agricultural area ber, November and December of 2012 and once in of the Podunajská pahorkatina Hills (17° 31’ 00’’ E, 48° March of 2013).The field work was carried out between 16’ 26’’ N). The area covers 18.7 km2, and the average September and March. Each counting started at 10 a. m. altitude is between 125–140 m. The major habitat is and only when the weather conditions were with no arable land with windbreaks (Table 1). Habitats change snow cover, fog, rainfall or strong wind (over 10 m/s). during the year in the area. The study area is a part of The visibility was often low in the early mornings the special protection area (SPA) Ulanska mokrad (NA- because of the fog. It often lasted until 10 a. m. The TURA 2000), which protects raptor species, such as the temperature did not fall below 0°C. The field method saker falcon (Falco cherrug), the Montagu’s harrier used was the point transect (Gibbons and Gregory (Circus pygargus), the black kite (Milvus migrans) and 2006). A total of 7 counting points were established. the red-footed falcon (Falco vespertinus). Points were located 700–1300 m apart and with the go- od view of the area. A binocular (10×42) was used to H a b i t a t s a v a i l a b i l i t y search for raptors and a monocular (30×65) for identify- Habitat categories were recorded with a GPS unit (Gar- ing raptors. Raptors were recorded within two kilomet- min eTrex 10) and a camera during the counting of the res. The habitat category was added only when I was number of raptors. For each counting habitats were sure where the raptor was hunting. The average distance recorded by making photo documentation from the between the counting points was 800 m. Each point was counting points. These were translated into GIS layers. sampled for 20 minutes. Only hunting birds of prey we- Eight habitat categories were classified in the monito- re selected for the study. I identified hunting birds as ring area – alfalfa, corn, fallow, wheat, beet & rape, birds perched on trees or on the ground, hunting with Tab. 1 . The cover of the habitats in the study area [%]. A – average, H’ – Shannon diversity index. Tab. 1 . Pokryvnosť biotopov v skúmanej oblasti [%]. A – priemer, H’ – Shannonov index diverzity. 2011 201 2 201 3 habitat type XI XII I IX XI XII III A alfalfa 4.2 3.2 3.2 6.6 8.8 8.8 8.8 6.2 corn 0.0 0.0 0.0 1 2.0 0.0 0.0 0.0 1 .7 rape and beet 9.8 7.4 7.4 0.0 3.36 3.4 3.4 5.0 wheat 42.9 42.9 42.9 0.0 35.2 35.1 35.1 33.4 ploughed field 22.3 43.6 46.2 41 .2 51 .6 51 .6 51 .6 44.0 stubbles 20.1 2.6 0.0 1 9.0 0.8 0.8 0.8 6.3 fallow 0.4 0.0 0.0 1 4.3 0.0 0.0 0.0 2.1 sunflower 0.0 0.0 0.0 6.6 0.0 0.0 0.0 0.9 H’ 1 .41 1 .1 2 1 .02 1 .57 1 .08 1 .08 1 .08 38 Slovak Raptor Journal 2013, 7: 37–42. DOI: 10.2478/srj-2013-0007. © Raptor Protection ofSlovakia (RPS) a hovering flight or circling, gliding with a prey attack. habitat preference of the common buzzard and of the Other types of flight (circling, gliding, direct flight wit- common kestrel. These species were the most common hout an attack) were not considered as hunting. I assig- raptors in this area. Data were analysed independently ned a category to the habitat where each individual for each species because of the slightly different habitat raptor was hunting. In the case of a flying raptor, I as- requirements of each species (Butet et al. 2010). Habitat signed the category of the habitat over which it was fly- diversity was calculated with the Shannon Diversity ing. All individual birds were recorded only once when Index. they were observed for the first time. Birds perched on trees between two habitats were assigned to the habitat Results being monitored by the raptor.