Acrocephalus 22 (108): 149 – 154, 2001 The breeding density of Eurasian Scops Owl Otus scops in urban areas of Pelje{ac Peninsula in southern Dalmatia Gnezditvena gostota velikega skovika Otus scops v urbanih okoljih polotoka Pelje{ac v ju`ni Dalmaciji Al Vrezec National Institute of Biology, Ve~na pot 111, SI-1000 Ljubljana, Slovenija, e-mail: al.vrezec@uni-lj.si In 1998, 18 human settlements in the area of 93 km2 were searched for the Eurasian Scops Owl Otus scops territories (calling males) on central Pelje{ac Peninsula (S Dalmatia, Croatia). The playback method was used. In all settlements, 90 singing males were counted, which indicates that the total urban breeding population of Eurasian Scops Owl on Pelje{ac Peninsula was around 345 pairs in 1998. According to the author’s opinion, the larger part of the Eurasian Scops Owl population breeds in the area within settlements. With a crude density of 10 – 15 pairs/10km2 and by considering the population dynamics recorded in the village of Kuna, the total population on Pelje{ac peninsula was estimated at 230 to 575 pairs. Further ecological densities for several clumps of urban populations are presented. Ecological densities have found to be very variable (0.6 – 9.3 calling males/10ha), with higher densities recorded in settlements on the mainland of Pelje{ac Peninsula. Ecological density did not correlate with the size of the settlement. Key words: Otus scops, Eurasian Scops Owl, crude density, ecological density, urban areas, Pelje{ac Peninsula, Croatia Klju~ne besede: Otus scops, veliki skovik, gostota, ekolo{ka gostota, urbana obmo~ja, polotok Pelje{ac, Hrva{ka 1. Introduction In Europe, the Eurasian Scops Owl Otus scops inhabits mainly semi-open cultural areas and normally avoids dense forests and open panoramas (Bavoux et al. 1997). The species is often mentioned as a breeding bird in orchards, the surroundings of vineyards, in park areas, gardens, and avenues (Glutz von Blotzheim & Bauer 1994). Especially in southern Europe it frequently breeds in avenues and gardens in or near settlements (Mikkola 1983). In the Mediterranean part of Europe the species presumably is the most tolerant owl concerning its habitat selection (Sara 1990). The population of the Eurasian Scops Owl in Croatia is supposed to be the second largest in Europe. It is estimated at 21,000 breeding pairs (Bavoux et al. 1997), and approximately 25% of the whole European population, but the accuracy of this estimate is not known (Bavoux et al. 1997). For example, Luka~ (1998) estimated only 1,000 to 5,000 pairs for Croatia, while Snow & Perrins (1998) referred, on the contrary, to a much higher figure for Croatia, i.e. 20,000-25,000 pairs. On the island of Krk (Kvarner Bay), a very high Eurasian Scops Owl’s ecological density was found (Mebs & Scherzinger 2000), indicating that Luka~ (1998) could have underestimated the Croatian population. In general, the Eurasian Scops Owl is widely distributed and a rather common species in coastal areas of Croatia (Kralj 1997, Rucner 1998). Except for some short contributions (Vrezec 2000 & 2001), no data on the Eurasian Scops Owl from Pelje{ac Peninsula have been published so far. The aim of this article is to contribute data on the density and abundance of Eurasian Scops Owls on Pelje{ac Peninsula with special reference to urban areas. H9 Al Vrezec: The breeding density of Eurasian Scops Owl Otus scops in urban areas of Pelje{ac Peninsula in southern Dalmatia 2. Study Area and Methods 2.1. Study Area Pelje{ac is a 355 km2 large peninsula in southern Dal-matia, Croatia (Figure 1), with 69 large settlements and villages (small isolated hamlets not included). The largest settlements are Orebi}, Trpanj, Janjina and Ston. The study area is situated in the central part of Pelje{ac Peninsula between the villages of Duba and oo oo Dra~e (43 01’ – 42 56’ N, 17 10’ – 17 29’ E). In an area of 93 km2, 18 settlements were investigated (with small hamlets included in some villages): Donja Vru}ica (with the hamlet of D. Selo), Dra~e, Duba, Gornja Vru}ica (only part of the village called Selo was investigated), Janjina, Ko{arni Do, Kuna, Oskoru{no (with the hamlet of Orhanovi}i), Pijavi~ino (part of the villages of D. Selo and Panteti}i), Popova Luka, Potomje (with the hamlets of Doci, Gruda and Jugovi}i), Prizdrina, Sreser, Trpanj (including the hamlet of Dekovi}i), Zagruda, Zakamenje, Zakotarac and @upanje Selo. Four villages are situated on the coast (Dra~e, Duba, Sreser and Trpanj), the rest in the mainland of Pelje{ac Peninsula. The area belongs to the Mediterranean phyto-geographical region with thermophilous evergreen forests of Holm Oak Quercus ilex, especially Orno- Quercetum ilicis and Ostryo-Quercetum ilicis. In degraded areas, e. g. garigue, Erico-Cistetum cretica is more common. Beside the already mentioned characteristic species of forest associations, the more common tree species found in the area are: Pinus halepensis, P. nigra dalmatica, P. pinaster, Acer monspes-sulanum, Quercus pubescens etc. (Jasprica & Kova~i} 1997, own data). The most important cultural plants in the area are olive tree and vine. 2.2. Method For owl censuses the playback method as suggested by Samwald & Samwald (1992) was used. The efficiency of playback was tested for some owls (e.g. Tengmalm’s Owl Aegolius funereus and Tawny Owl Strix aluco; Holmberg 1979, Redpath 1994), but there is no data available for the Eurasian Scops Owl. The efficiency of playback can be extremely variable between owl species (Zuberogoitia & Campos 1998). So far we can only speculate on the efficiency of this method for the discussed species. Still, Eurasian Scops Owls react intensively to playbacks if played near their territories (Zuberogoitia & Campos 1998). For the present study I censused owls in the urban areas only. Count points were selected on exposed sites, where the whole area of the settlement could be covered. Position of every singing male was drawn into the map to Duba D. Vručicaf • Trpanj • G. Vručica Zagrudao ^^"f™ Kosami Do • #županje»!}0una Zakotarac« #Prizdrina °Zakamenje Potomje» ¦ Pijavičino Sreser Janjina i oDrače t Popova Luka Figure 1: Study area of Pelje{ac Peninsula (S Dalmatia, Croatia) with marked human settlement that were searched for Eurasian Scops Owls, with the size of dots delineating ecological density (calling males/10 ha) Slika 1: Obravnavano obmo~je polotoka Pelje{ac (ju`na Dalmacija, Hrva{ka) z ozna~enimi naselji, kjer je bil opravljen popis velikih skovikov. Velikosti pik ponazarjajo ekolo{ke gostote (pojo~i samci/10 ha). 150 ACROCEPHALUS 22 (108): 149 — 154, 200I avoid doubling. Presumably, all territorial males within the settlements investigated could be counted with the aid of the described method. Each settlement was visited once a year. Census work was carried out in spring time 1998 from the end of April to the beginning of May, which seems to be the best time for censusing Eurasian Scops Owls (Zuberogoitia & Campos 1998, Denac 2000, [tumberger 2000). Weather conditions could have affected vocal activity of owls significantly (Clark & Anderson 1997, Zuberogoitia & Campos 1998), so fieldwork was performed only on calm and clear nights. Additional censuses took place in 1997, 2000 and 2001, but not all settlements were included in those years. As reference areas for the calculation of ecological densities, the entire area of the settlements including non-urban and rural habitats in its immediate vicinity (gardens, parks, avenues, surrounding vineyards, etc.) was used. The correlation between ecological density and size of the settlements was tested with the Pearson correlation coefficient. The size of the Eurasian Scops Owl population in urban areas for the whole Pelje{ac Peninsula was estimated by using the average number of owls Table 1: Results of the Eurasian Scops Owl Otus scops calling males census in settlements of Pelje{ac Peninsula for the years 1997, 1998, 2000 and 2001 (-- = no data) Tabela 1: Rezultat popisa pojo~ih samcev velikega skovika Otus scops v vaseh Pelje{ca v letih 1997, 1998, 2000 in 2001 (-- = ni podatka) Settlement/ Naselje 1997 1998 2000 2001 counted in the investigated settlements extrapolated to the whole number of settlements in the area. Differences between sampling area and the whole area of the Peninsula in proportion to human settlements situated on the coast were tested with ?2-test. 3. Results During 1998, 90 calling males of Eurasian Scops Owl were counted in 18 settlements of central Pelje{ac Peninsula (Table 1). On the average, 5.0 ± 4.8 calling males were found per settlement. Settlements with large numbers of Eurasian Scops Owls were surrounded with cultivated areas, mostly by vineyards and gardens. The highest Eurasian Scops Owl ecological densities were found in Prizdrina (9.3 calling males/10ha) and Gornja Vru}ica (8.3 calling males/10ha), the lowest at Sreser (0.6 calling males/10ha), Duba (0.8 calling males/10ha) and Table 2: Overview of settlement sizes, altitudes and breeding densities of the Eurasian Scops Owl Otus scops calling males in urban habitats of central Pelje{ac Peninsula in 1998 Tabela 2: Pregled velikosti naselij, nadmorskih vi{in in gostot pojo~ih samcev velikega skovika Otus scops v urbanih okoljih na osrednjem delu Pelje{ca v letu 1998 Settlement/ Altitude/ Area/ Ecol. density/ Naselje Nadm. vi{ina Povr{ina Ekol. gostota (m) (ha) (calling males/10ha) Donja Vru}ica 3 - Dra~e 0 - Duba 1 - Gornja Vru}ica 12 - Janjina 7 - Ko{arni Do 1 - Kuna 10 15 25 24 Oskoru{no 9 9 9 Pijavi~ino 5 7 - Popova Luka 4 - Potomje 12 14 - Prizdrina 7 5 5 Sreser 1 - Trpanj 9 - Zagruda 0 1 - Zakamenje 0 3 - Zakotarac 1 - @upanje selo 3 2 - Donja Vru}ica 180 12,1 2,5 Dra~e 0 13,0 0,0 Duba 3° 12,4 0,8 Gornja Vru}ica 130 14,5 8,3 Janjina 120 35,5 2,1 Ko{arni Do 320 3,5 2,9 Kuna 370 64,1 2,3 Oskoru{no 300 21,4 4,2 Pijavi~ino 290 30,6 1,6 Popova Luka 120 9,8 4,1 Potomje 270 72,3 1,7 Prizdrina 320 7,5 9,3 Sreser 0 17,7 0,6 Trpanj 0 93,6 1,0 Zagruda 280 5,0 0,0 Zakamenje 320 4,2 0,0 Zakotarac 290 2,7 3,7 @upanje selo 280 7,2 4,2 AV. / povp. 23,7 2,7 SD / std. odklon 26,4 2,6 151 Al Vrezec: The breeding density of Eurasian Scops Owl Otus scops in urban areas of Pelje{ac Peninsula in southern Dalmatia Trpanj (1.0 calling males/10ha) (Table 2). The latter three villages are situated on the coast (Figure 1). Ecological density did not correlate with the size of the settlement (R = -0.22, ns). 30 25 20 15 10 I! °>* 5 1997 1998 1999 2000 2001 Figure 2: Population dynamics of Eurasian Scops Owl Otus scops in the years 1997, 1998, 2000 and 2001, as established in the village of Kuna in central part of Pelje{ac Peninsula (in 1999, census was not carried out) Slika 2: Populacijska dinamika velikega skovika Otus scops v letih 1997, 1998, 2000 in 2001 v vasi Kuna v osrednjem delu Pelje{ca (v letu 1999 ni bilo popisa) In the village of Kuna, a long-term study on the Eurasian Scops Owl numbers was carried out. The population increased for at least 2/3 during the 1997 to 2001 period (Figure 2), but no significant changes could be found in other villages, e.g. Oskoru{no and Prizdrina (Table 1). The sampling area was representative for the entire Pelje{ac Peninsula with 1.9 settlements/10km2, the same as on the whole of Pelje{ac Peninsula. Of the 18 investigated human settlements, four were situated on the coast (22%). On the entire Pelje{ac Peninsula more settlements are situated on the coast (38%), but differences with sampling area were not significant (?2=1.5, ns). According to my calculations, around 345 breeding pairs may have bred in 1998 in all urban areas of the entire Pelje{ac Peninsula. 4. Discussion The present study was restricted to the breeding population of the Eurasian Scops Owl on Pelje{ac Peninsula, with special emphasis on its ecological densities in human settlements. According to accidentally collected data, I speculate that the main Table 3: Comparison of data on the Eurasian Scops Owl Otus scops crude and ecological densities (data converted into calling males/10ha) Tabela 3: Primerjava podatkov o splo{nih in ekolo{kih gostotah velikega skovika Otus scops (podatki so prera~unani na enoto pojo~i samci/10ha) Location / Lokacija Density /Gostota Reference area/ Source / Vir (calling males/10ha) Referen~na povr{ina Crude density Croatia (Pelje{ac) o.i - 0.15 93 km2 this work / to delo Slovenia (Gori~ko) 0.05 442 km2 Štumberger (2000) Slovenia (Ljubljansko barje) 0.02 - 0.04 163 km2 Senegačnik (1998), Denac (2000) Austria (Steiermark) 0.005 204 km2 Samwald & Samwald (1992) Slovakia (Krupinska planina) 0.008 150 km2 Glutz von Blotzheim & Bauer (1994) France (Ile d'Oleron) 0.03 - 0.04 175 km2 Bavoux et al. (1991) Ecological density Croatia (Pelje{ac) 0.6 - 9.3 2.7 - 93.6 ha this work / to delo Croatia (Krk)1 50.0 2 ha Glutz von Blotzheim & Bauer (1994) Slovenia (Gori~ko) 0.2 - 0.6 1 - 25 km2 Štumberger (2000) Austria (S Tyrol)1 50.0 1 ha Glutz von Blotzheim & Bauer (1994) Austria (Steiermark) 0.3 2.4 km2 Samwald & Samwald (1992) Swizerland (Valais central) 1.7 - 2.4 100 ha MEBS & SCHERZINGER (2OO0) Italy (NE Italy) 0.2 - 0.4 400 ha Bavoux et al. (1997) Romania (Reghin)1 83.0 0.6 ha Glutz von Blotzheim & Bauer (1994) France (Port-Cros) 0.4 - 0.5 306 ha Glutz von Blotzheim & Bauer (1994) See the text for explanation / za razlago glej besedilo 152 ACROCEPHALUS 22 (108): 149 — 154, 200I part of the Pelje{ac Peninsula population is actually concentrated in urban areas and their surroundings, for which I have two explanations: (1) large areas of Pelje{ac Peninsula are covered with dense forests (which are unsuitable for the species Bavoux et al. 1997), and (2) due to roadside lamps, which are mainly restricted to settlements and attract large numbers of insects, the density and availability of large insects are higher in and around human settlements. Therefore the total number of breeding pairs for the entire area of Pelje{ac Peninsula is probably not significantly higher than the calculated one (345 pairs). According to the population dynamic recorded in the village of Kuna, we could conclude that total size of the Eurasian Scops Owl population on Pelje{ac Peninsula is between 230 to 575 pairs. Estimate of crude density of the species population on the Peninsula amounts to 10 - 15 pairs/10km2. These are very high values in comparison to other studies (Table 3), indicating that the Eurasian Scops Owl is a very common and well distributed bird species on Pelje{ac Peninsula. One of the characteristics of the species is that it can be locally very concentrated in some areas (Cramp 1985) or it can form calling groups ([tumberger 2000). All high estimates of breeding densities published in literature were acquired from such clumps. Densities in clumps are higher than those calculated for larger areas; > 50 km2 (Table 3), so densities of clumps could be treated as ecological density (the number per unit of habitat space -available area that can actually be colonised by the population; Odum 1971). Ecological densities of Eurasian Scops Owls established on Pelje{ac in different clumps (e.g. breeding population in settlements) are high to middle ranged in comparison with values from other studies (Table 3). Extremely high ecological densities on the island of Krk (Croatia), in S Tyrol (Austria) and Reghin (Romania) were acquired from small sized reference areas ranging in size from 0.6 to 2 ha, which could be the reason for the extreme density values in these areas. Due to the suitability of surrounding habitats of the settlements investigated on Pelje{ac, ecological densities in clumps were highly variable (0.6 – 9.3 calling males/10ha). From the collected data it can be concluded that settlements inside the Peninsula (1.6 – 9.3 calling males/10ha) are more suitable than those on the coast (0.6 – 1.0 calling males/10ha). The results proved that ecological density was not correlated with the size of the settlements, so other ecological parameters seem to be more important. The highest ecological densities were recorded in settlements surrounded by extensive cultivated landscapes mixed with maquis and small woods, which seems to be, according to many other researchers, the most suitable breeding habitat for this typically Eastern European-Mediterranean species (Mikkola 1983, Cramp 1985, Sara 1990, Mebs & Scherzinger 2000). Acknowledgements: My sincere thanks go to Borut Rubini~ for his help during fieldwork, to Dr. Davorin Tome for his critical remarks on the manuscript, and to Milijan Ši{ko for preparing a map. 5. Povzetek Leta 1998 so bili na polotoku Pelje{ac (ju`na Dalmacija, Hrva{ka) popisani pojo~i samci velikega skovika Otus scops v 18 naseljih na obmo~ju, velikem 93 km2. Uporabljena je bila metoda izzivanja s posnetkom. Pre{tetih je bilo 90 pojo~ih samcev velikega skovika. Avtor ocenjuje, da je populacija velikih skovikov, gnezde~ih v urbanih okoljih, leta 1998 na celotnem polotoku {tela okoli 345 parov, ki naj bi po njegovem mnenju sestavljala tudi ve~ji del na Pelje{cu gnezde~e populacije z ocenjeno gostoto 10 – 15 parov/10km2. Celotna populacija velikega skovika na Pelje{cu je ocenjena na 230 do 575 parov. V delu so predstavljene tudi ekolo{ke gostote urbano gnezde~e populacije v razli~nih skupinah. Ekolo{ke gostote so med skupinami zelo nihale (0.6 – 9.3 pojo~ih samcev/10ha), vendar so bile skupine z vi{jimi ekolo{kimi gostotami najdene le na celinskem delu polotoka. V raziskavi soodvisnost med velikostjo naselja in ekolo{ko gostoto ni bila potrjena. 6. References Bavoux, C., G. Burneleau & P. Nicolau-Guillaumet (1991): Aspects de la biologie de reproduction du Hibou petit-duc Otus scops. Alauda 59 (2): 65-71. Bavoux, C., G. Burneleau & P. Nicolau-Guillaumet (1997): Scops Owl Otus scops. In: Hagemeijer, W.J.M. & M.J. Blair (eds.): The EBCC Atlas of European Breeding Birds. T & AD Poyser, London. Clark, K.A. & S.H. Anderson (1997): Temporal climatic and lunar factors affecting owl vocalizations of western Wyoming. J. Raptor. Res. 31 (4): 358-363. Cramp, S. (eds.) (1985): Handbook of the Birds of Europe, the Middle East and North Africa, The Birds of the Western Palearctic. Vol. I V. Oxford University Press, Oxford, New York. Denac, K. (2000): Rezultati popisa velikega skovika Otus scops na Ljubljanskem barju v letu 1999. Acrocephalus 21 (98-99): 35-37. 153 Al Vrezec: The breeding density of Eurasian Scops Owl Otus scops in urban areas of Pelje{ac Peninsula in southern Dalmatia Glutz von Blotzheim, U.N. & K.M. Bauer (1994): Handbuch der Vögel Mitteleuropas, Bd. 9, Columbi-formes – Piciformes. AULA-Verlag, Wiesbaden. Holmberg, T. (1979): Point transect census of Tengmalm’s Owl – a methodological study. Var Fagelvärld 38: 237-244. Jasprica, N. & S. Kova~i} (1997): Vascular flora of the central part of Pelje{ac peninsula. Nat. Croat. 6 (4): 381-407. Kralj, J. (1997): Ornitofauna Hrvatske tijekom posljednjih dvjesto godina. Larus 46: 1-112. Luka~, G. (1998): List of Croatian Birds. Nat. Croat. 7 (Suppl. 3): 1-160. Mebs, T. & W. Scherzinger (2000): Die Eulen Europas. Franckh-Kosmos, Stuttgart. Mikkola, H. (1983): Owls of Europe. T & AD Poyser, Calton. Odum, E.P. (1971): Fundamentals of Ecology. W.B. Saunders Company, Philadelphia, London, Toronto. Redpath, S.M. (1994): Censusing Tawny Owls Strix aluco by the use of imitation calls. Bird Study 41: 192-198. Rucner, D. (1998): Ptice hrvatske obale Jadrana. Hrvatski prirodoslovni muzej, Ministarstvo razvitka i obnove, Zagreb. Samwald, O. & F. Samwald (1992): Brutverbreitung und Bestandsentwicklung der Zwergohreule (Otus scops) in der Steiermark. Egretta 35 (1): 37-48. Sara, M. (1990): Aspetti della nicchia ecologica degli strigiformi in Sicilia. Naturalista sicil. S. I V, XIV (suppl.): 109-122. Senega~nik, K. (1998): Popis velikega skovika Otus scops na Ljubljanskem barju. Acrocephalus 19 (90-91): 143-146. Snow, D.W. & C.M. Perrins (eds.) (1998): The Birds of the Western Palearctic 1, Non-Passerines. Oxford University Press, Oxford, New York. [tumberger, B. (2000): Veliki skovik Otus scops na Gori~kem. Acrocephalus 21 (98-99): 23-26. Vrezec, A. (2000): Veliki skovik Otus scops in ~uk Athene noctua. Acrocephalus 21 (98-99): 85. Vrezec, A. (2001): Veliki skovik Otus scops. Acrocephalus 22 (106-107): 131. Zuberogoitia, I. & L.F. Campos (1998): Censusing owls in large areas: a comparison between methods. Ardeola 45 (1): 47-53. Arrived / Prispelo: 6.1.2002 Accepted / Sprejeto: 28.1.2002 154