Magpie (Pica pica) Population Density and Habitat Distribution in the City of Sofia

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1 In: Penev L., J. Niemelä, D. J. Kotze & N. Chipev (Eds.) Ecology of the City of Sofia. Species and Communities in an Urban Environment, pp , PENSOFT Publishers, Sofia-Moscow Magpie (Pica pica) Population Density and Habitat Distribution in the City of Sofia Nevena T. Kamburova Central Laboratory of General Ecology, 2 Gagarin Street, Sofia, Bulgaria larus@abv.bg SUMMARY Research on the Magpie (Pica pica) was carried out in the territory of Sofia during the summer periods of 1998/99, and the winter periods of 1997/98 and 1998/99. The number of breeding Magpies was estimated to be 690 pairs. Density of the pairs varied widely, between 0,07 and 3,04 pairs/10ha. The average density for the entire study area was 0,41 pairs/10ha. The density of breeding Magpies in the seven investigated habitat types ranged from 0,09 to 1,59 pairs/10ha and the highest density was recorded in natural biotopes and in riverside belts. It, there fore, appears that Magpies colonize the city along natural corridors, i.e. rivers and parks. Breeding Magpies were scarce (0,09 pairs/10ha) in the city centre, probably because of human pressure and living conditions in Sofia. KEY WORDS: Magpie Pica pica, breeding density, habitat distribution, urban habitat INTRODUCTION In Bulgaria Magpie is a common bird species in urban habitats, such as cities, towns and rural areas (Donchev, 1958). Although anthropogenic landscapes of big cities are not typical living conditions for this species, it has succeeded in adapting to some new habitat types created by humans. According to Nankinov (1981,1982) and Iankov (1983) the mass movement of Magpies into anthropogenic landscapes of towns and villages began in the 1960-s, mostly along river valleys and suburban parks. Many European authors (Tatner, 1982; Bokotey, 1997; Gorski, 1997; Jersak, 1997; Witt, 1997) noted that the population density of Magpie was highest in parks and city suburbs and gradually increased in central parts of the cities/towns. The colonization of new urban territories appeared to be mainly along natural ecological corridors (rivers and parks), moving from the periphery of cities to its centre. The aims of this research were to obtain information on population density of Magpies in the territory of Sofia and to map Magpie pairs in different habitats in Sofia. 451

2 MATERIALS AND METHODS This present study was carried out in the territory of the city of Sofia. The size of the study area was approximately 170 square kilometers. Field observations were made from November 1997 to May Fieldwork was mainly conducted during the Magpie breeding period. Territory mapping was used to estimate Magpie number and density. The study area was divided into 180 UTM grid squares 1 km 2 each (Iankov, 1983). Standardized sampling took place in each grid square. The number of breeding Magpies was determined on the basis of built and inhabited nests, and most position was marked on the map. Observations were made during the morning (between 8 and 11 o clock) and in the afternoon (between 4 and 6 o clock). Each plot was visited at least twice. I also calculated the density of breeding Magpies in pairs per 10ha. A similar study was conducted by Iankov (1983) and I compared his nests density reported in 117 plots with the number of nests found here. Seven biotopes were defined to determine the density of breeding pairs Magpies in different habitats of the city, i.e housing estates, open areas, natural and modified riverside belts, parks and gardens, industrial zone, rural zone and the city centre. RESULTS AND DISCUSSION Density of breeding pairs in plots 690 breeding pairs were reported in Sofia. The highest density reported was 3,04 pairs/10ha and the lowest was 0,07 pairs/10ha. Density differences are shone in (Fig. 1). The highest density was recorded in plot J16 3,04 pairs/10ha. This square covers an industrial district, a small part of a housing estate and a large part of an open area. Its high density was due to the presence of a large number of suitable sites for nesting, i.e. tall tree species (Populus sp.) in the yards of the industrial complexes. The open areas in this square finding provide possible food sources. Nineteen plots had no breeding pairs, while three plots were characterised by low Magpie density. These plots cover two zones in the territory of the city with exceptionally low density. One of these zones is the central part of the city of Sofia. The low density and absense of breeding pairs here are due mainly to the following factors: a/ densely built-up area with little natural habitat, b/ insufficient number of trees suitable for nesting and c/ absence of places for finding food. The second zone was the southwest part of the city that includes housing estates with low buildings (houses and villa districts). These housing estates are located in thick forestlands, avoided by Magpies. In the remaining plots the density of breeding pairs varied between 0,11 and 1,59 pairs/10ha. 452

3 Iankov (1983) studied distribution of Magpie in Sofia reported 268 pairs in 117 plots. 564 pairs were reported in these plots a more than doubling in pairs over a 17-year period. This increase was probably gradual and is likely to continue in the future, since non-breeding Magpie has regularly been observed in the central parts of the city. In 80% of the plots compared, a considerable increase (four times) in number of breeding pairs was observed (from 1983 to 1999), and in only 20% of the plots there was a decrease during this time of period. The decrease is most likely explained by an increase in building-up areas and human settlement. Nevertheless, our data showed mass colonization by Magpies in Sofia City. My results are in agreement with other studies done in Europe. For example, in Berlin Witt (1997) showed a density increase in Magpies of more than three times over a seven year period. In Lvov (Ukraine) the density of breeding Magpies was 0,8 pairs/10ha (Bokotey, 1997). In Poland Gorski (1997) studied 11 towns and 6 areas of farmland in Koszalin Region. Gorski reported that the breeding population of the Magpie in towns almost doubled in the period between and in In Warsaw the density of breeding Magpies was estimated to be 0,6-0,8 pairs/10ha (Luniak et al., 1997). Density of breeding Magpies in different habitat types Various habitat types are presented in big cities, with some still in their original condition (river banks in the suburbs), and others characterised by natural vegetation (parks and forest parks). Other parts are completely changed (housing estates, city centre) or have originated as a specific anthropogenic region (industrial zones). Magpie distribution was studied in seven different biotopes of the anthropogenic landscape. Housing estates This biotope is characterized by multi-storeyed buildings, streets, lanes, open-air kindergartens as well as various tree species. Newly built housing estates and houses built about years ago are also in this biotope type. Five plots had a highest density of Magpies (between 2,04 and 3.04 pairs/10ha). These plots include parts of old housing estates with a many suitable nest sites and grassy areas nearby, suitable for finding food. Most of the plots in this biotope had relatively low breeding densities (0,13-0,96 pairs/10ha) with the biotope average being 0,38 pairs/10ha. This low value is possibly because of the density built-up nature of this biotope. There are suitable sites for nesting, but there appear unattractive for Magpies. 453

4 N B4 B5 B6 B7 B8 B9 B10 B11 C3 C4 C5 C6 C7 C8 C9 C10 C11 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 0 E2 E3 E4 E5 E6 E7 E8 E9 E10 E11 E12 E13 E14 E15 E16 E17 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 G12 G13 G14 G15 G16 G17 H2 H3 H4 H5 H6 H7 H8 H9 H10 H11 H12 H13 H14 H15 H16 H17 I 1 I 2 I 3 I 4 I 5 I 6 I 7 I 8 I 9 I 10 I 11 I 12 I 13 I 14 I 15 I 16 I 17 J1 J2 J3 J4 J5 J6 J7 J8 J9 J10 J11 J12 J13 J14 J15 j16 J17 L1 L2 L3 L4 L5 L6 L7 L8 L9 L10 L11 L12 L13 L14 L15 L16 L17 M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 N3 N4 N5 N6 N7 N8 N9 N10 N11 N12 N13 N14 O10 O11 O12 O13 O14 P12 P13 P14 0,01-0,50 0,51-1,00 1,01-1,50 1,51-2,00 over 2,00 Fig. 1. Magpie density (pairs/10 ha) in the territory of Sofia City Open areas Open areas are expansive areas among housing estates and in the suburbs, characterised by grassy vegetation with some trees.the average density of breeding pairs of Magpies here was 0,26 pairs/10h, which is about half the value of average of the whole area studied. This is mainly because of a lack of trees appropriate for nesting. Open areas were often visited by Magpies to find food and nest materials. Natural and modified riverside belts This biotope with its riverside vegetation and its adjacent green areas provides an environment similar natural habitats of Magpies, and was therefore one of the most attractive biotopes for Magpies. The highest density of breeding pairs (1,59 pairs/10ha) was observed here, which was almost four times higher than the study area average (0,41 pairs/10ha). The highest density of Magpie pairs was observed along the riverbanks of Suhodolska and Darvenishka rivers (between 6,38 and 20,83 pairs/10ha). These areas were also favorable for Magpies since they pass through 454

5 housing estates and rural houses where additional sources of food are found. Colonization of new territories in the city seems to take place along natural corridors, i.e. rivers and parks, dispersing from the periphery to the city centre (Nankinov, 1982; Iankov, 1983). Parks and gardens This biotope is quite similar to natural habitats of Magpies. A high density of breeding pairs was observed in four small parks. It is a proof that Magpies prefer single or small groups of trees located near open areas. For example, a high-pair density was in Yuzhen Park (1,00 pairs/10ha) which is characterized by woody areas alternating with open areas. Parks without open areas, however, had low Magpie pair-density ( Loven and Zapaden parks). The mean density of Magpies for this biotope was 0,37 pairs/10ha. Salaj (1991) also noted that the highest density of Magpie nests was in gardens and cemeteries of villages and lowest in town centres. Industrial zone This biotope is not typical for Magpies, there are many big buildings, noisy area and poor vegetation, and nevertheless some Magpies occurred here. However in Sheffield (England) in 1977, a study showed that the only territory where Magpies were missing or their density was very low was the industrial districts of towns (Gilbert, 1991). In spite of that the author observed a quick invasion of Magpies in unfavorable industrial regions. In the present study, the density of breeding pairs in this biotope was 0,59 pairs/10ha, one of the highest in the area studied. Possible reasons include, the availability of single and small groups of poplars (Populus sp.), preferred by Magpies for nesting, and large grassy territories located nearby which are appropriate for finding food. Rural zone This biotope is characterized by one-family houses with big yards, grassy areas, shrubs and various fruit trees, and also appears to be one of the most favorable areas for Magpies. In this biotope the highest number of breeding pairs (182 numbers) was recorded. This area was large (3175,62 ha), and the density of Magpie pairs was therefore relatively low, 0,57 pairs/10ha. One of the most important factors for the settlement of Magpies in this biotope is the possibility of finding food near houses and in agricultural areas. City centre The city centre is a densely built-up area, with few open areas between buildings. The ground surface is covered with asphalt, pavement and other solid materials, with almost no green spaces with vegetation. It is therefore, not surprising that the density of breeding pairs in this biotope was very low, i.e. 0,09 pairs/10ha. This very low density of breeding pairs in the centre of Sofia is due to strong human pressure caused by vehicles, noise, air pollution, and the absence of nesting and 455

6 feeding sites. Bokotey (1997) showed that the highest density of breeding Magpies was in parks and in areas of one-family houses (1,2 pairs/10ha), and the lowest in city centre and industrial districts (0,4 pairs/10ha). ACKNOWLEDGEMENTS I want to thanks to Prof. B. Ivanov for valuable and useful advice during the research. Dr. P. Iankov for his participation in the inventory work, my colleagues who helped me in field investigations, and my sister for translating this manuscript into English. REFERENCES Bokotey, A Numbers and distribution of the Magpie (Pica pica) in Lvov (Ukraine). Acta Orn. 32: 5-7 Donchev, S Materials on taxonomy, ecology and biology of crow (Corvidae) in Bulgaria. Proceedings of the Institute of Zoology, BAS 7: (in Bulgarian). Gilbert O. L The Ecology of Urban Habitats. Chapman and Hall, London, 325 pp. Gorski, W Urban and rural populations of the Magpie (Pica pica) in Koszalin Region, NW Poland. Acta Orn. 32: Iankov, P Sofia ornithofauna, special features of its structure and development. Belarusia Zoology Institute (Ph. D. thesis). 238pp. (in Russian). Jerzak, L Magpie nest sites in urban habitats in Poland. Acta Orn. 32: Luniak, M., Kozlowski, P & Nowicki, W Magpie (Pica pica) in Warsaw abundance, distribution and changes in its population. Acta Orn. 32: Nankinov, D Stages in urbanization and synanthropization of Bulgarian birds. Ornith. Inform. Bull. 10: 9-29 (in Bulgarian). Nankinov, D The birds of Sofia City. Ornith. Inform. Bull. 12: (in Bulgarian). Salaj, J The vertical distribution and location of the synanthropical population of Magpie (Pica pica) in the basins of Southern Slovakia. Biologia Bratislava 46, 6: Tatner, P Factors influencing the distribution of Magpie (Pica pica) in an urban environment. Bird Study 29: Witt, K On the abundance of Magpie (Pica pica) during breeding and winter season in Berlin. Acta Orn. 32: