Magpie Pica pica nest sites in farmland in vicinity of Wrocław city (SW Poland)

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1 Jerzak L., Kavanagh B.P., Tryjanowski P. (red.) Ptaki krukowate Polski [Corvids of Poland] Bogucki Wyd. Nauk., Poznań 2005 Grzegorz Orłowski Magpie Pica pica nest sites in farmland in vicinity of Wrocław city (SW Poland) Gniazdowanie sroki Pica pica w krajobrazie rolniczym okolicwrocławia ABSTRACT: In winter 2001/2002 in intensively managed farmland (57.5 km 2 ; 91% occupy by arable land) in the in vicinity of Wrocław city (Lower Silesia Province, south-western Poland) 56 nests of Magpie Pica pica were found. Eighty-two percent (46 nests) were located in the villages. The remaining 10 (18%) were found in open agricultural areas. The mean density of nests in built-up areas was 53 times higher that in crop fields (10.1 pairs/km 2 villages vs pairs/km 2 open farmland). Nests were found in 24 of 26 settlements examined. Density in particular settlements ranged from 0 to 200 pairs/km 2. Nests were located on 14 tree and 2 bush species. Nearly 22% of the nests were located in poplar trees Populus spp. The mean height of nests location in village areas was nearly twice that in open farmland (mean ± SD = 11.1 ± 3.7 m in villages vs. 5.7 ± 2.9 m in open farmland). Compared previous data from originating from an area of 15.8 km 2 situated in the middle part of the area studied, a 2 3-fold decrease in magpie population was recorded (decrease in density, from to 0.32 pairs/km 2 in the respective period). This would indicate a withdrawal of the species from open agricultural areas, while remaining at the former level in villages. KEY WORDS: Magpie, Pica pica, nest sites, farmland birds, agricultural intensification STRESZCZENIE: W ostatnich kilkudziesięciu latach na terenach zurbanizowanych Europy zanotowano znaczny wzrost liczebności sroki. Dane z krajów Europy zachodniej jak i Polski wskazują także na wzrost liczebności sroki na obszarach wsi, przy równoczesnym wyraźnym spadku liczebności w obrębie agroekosystemów, skąd gatunek ten wycofuje się. W krajach Grzegorz Orłowski, Department of Agricultural Bases for Environmental Management, Agricultural University of Wrocław, pl. Grunwaldzki 24, Wrocław. Poland, orlog@poczta.onet.pl

2 510 Grzegorz Orłowski Europy zachodniej regres liczebności sroki w obrębie pól uprawnych obserwowany jest od lat sześćdziesiątych XX wieku. Współcześnie, w wielu rolniczych rejonach Europy zachodniej sroka już nie występuje. Zimą 2001/2002 roku na intensywnie użytkowanej rolniczo powierzchni (57,5 km 2, w tym 91% zajmowały pola uprawne) położonej w okolicach Wrocławia (południowo-zachodnia Polska) zlokalizowano 56 gniazd sroki. Spośród 26 skontrolowanych osiedli gniazda sroki stwierdzono w 24 (92%) z nich. Średnie zagęszczenie gniazd na obszarze zabudowanym było 53-krotnie wyższe w porównaniu z terenami rolniczymi (10,1 pary/km 2 wsie vs pary/km 2 tereny rolnicze). Gniazda ulokowane były na 13 gatunkach drzew i krzewów. Średnia wysokość umieszczenia gniazd na terenie wsi była blisko dwukrotnie wyższa w porównaniu z otwartym krajobrazem rolniczym. W porównaniu z latami , na 15,8 km 2 powierzchni zlokalizowanej wewnątrz obszaru badanego na przełomie lat 2001/2002, zanotowano 2 3-krotny spadek zagęszczenia populacji lęgowej sroki. Gatunek ten wycofał się głównie z terenu pól uprawnych, a pozostał w niezmienionej liczbie we wsiach. Podobnie jak w przypadku innych gatunków ptaków występujących w agroekosystemach zanik śródpolnych populacji sroki spowodowany jest najprawdopodobniej zmianami w jakości środowiska, w tym zanikiem bazy pokarmowej, w wyniku intensyfikacji produkcji rolniczej. W świetle wyników uzyskanych w krajobrazie rolniczym okolic Wrocławia i innych rejonach Polski, można spodziewać się dalszego wycofywania się sroki z terenów pól uprawnych. Sroka jednak, w przeciwieństwie do innych ptaków związanych z agroekosystemami, nie jest gatunkiem potencjalnie zagrożonym, zważywszy na jej liczne występowanie na obszarach zurbanizowanych i postępujący wzrost liczebności w tym środowisku. SŁOWA KLUCZOWE: sroka, Pica pica, miejsca gniazdowe, krajobraz rolniczy, intensyfikacja rolnictwa Introduction There has been a considerable increase in the numbers of magpies Pica pica across Europe since the end of the second world war (Birkhead 1991, Jerzak 2001). Data from Western Europe and Poland indicate at an increase in magpie populations in the urban areas, concurrent with a decrease within agroecosystems (Gregory & Marchant 1995, Dombrowski 1997, Górski 1997, Siriwardena et al. 1998). In Poland the abundance of the magpie population in urban areas, mainly towns, has been well documented (Jerzak 2001, Tomiałojć & Stawarczyk 2003). In spite of the large number of quantitative data from farmland of Poland (review by Dombrowski 1997), there has been a lack of long-term studies on changes in the numbers of that species in such areas. In the period of intensive transformations in farming systems in Poland, it seems necessary to determine the present state of natural resources, including the bird fauna of farmland areas, and to monitoring the ongoing qualitative and quantitative changes in their structure. The aim of this work was to determine the abundance of the magpie population and characterize its nesting sites (used tree species, height of nest sites) in a fragment of the Wrocław Plain under the intensive of agricultural practises.

3 Magpie Pica pica nest sites in farmland in vicinity of Wrocław city (SW Poland) 511 Study area and methods The study area (57.5 km 2 ) is situated within two mezoregions of Primordial Valley of the Odra and Wrocław Plain, which belong to a greater physiographic unit of Silesian Lowland (Kondracki 1988). The predominant land use was arable land, which occupied about 91% of the area (52.32 km 2 ). This area was characterized by the lowest share of forests and woodlots in Poland, which amounted to 1.3%. The 26 villages surveyed occupy an area of 4.56 km 2 (7.9% of all surveyed area). Their area ranged from to 1.01 km 2 (average ± SD = 0.19 ± 0.23 km 2 ). Owing to the good and very good quality of the soil, most of the area is under intensive farming. Commodity farms prevail, at times exceeding 100 ha, especially in the western and southern parts of the study area. Medium size, farms of a few hectare remained mostly around the villages. In the year 2000, the largest crop area was wheat (50%), rape (25%), root crops (10%) and maize (8%). The location of Magpie nests (including species of nesting tree and height of nest) was recorded in the winter of 2001/2002. Nests were counted as originating from the last breeding season (2001), if a roof or its remnants could be seen. Searching for occupied nests, conducted on part of the area (15.8 km 2 see Fig. 1) in the consecutive breeding season (2002), indicated that the number of nests occupied was the same (n = 5) as in winter season. This may indicate that the number of nests spotted in winter season corresponds to actual number of breeding pairs. According to Fassola and Brichetti (1983), data on the numbers of magpie nests collected in winter time after a breeding season can be by 5% lower than actually existing. However, in that period it is markedly easier to spot the nests in trees devoid of leaves (Górski 1989). Results Atotal of 56 nests was located (density 0.97 pairs/km 2 ), including 46 nests (82%) located in village (settlements) areas (Fig. 1). The remaining 10 (18%) nests were found outside built-up areas. Magpie nests were found in 24 (92%) of the 26 surveyed settlements. The difference in the number of nests located in built-up areas and open spaces was statistically significant (c 2 = 46.29; df = 1, p < 0.001). Apositive, statistically significant correlation was found between village area and the number of nests located in its precincts (r s = 0.66, p < 0.001, n = 26). The mean density of nests in built-up areas was 53 times higher that in agricultural areas (10.1 pairs/km 2 villages vs pairs/km 2 farmland). Density in particular settlements ranged from 0 to 200 pairs/km 2 (for 26 villages the mean ± SD was 33.7 ± 61.6 pairs/km 2 ). Anegative statistically significant correlation was found between village area and density of nests localized in its precincts (r s = 0.67, p < 0.001, n = 26). Nests were located on 14 tree and 2 bush species (Table 1). Nearly 22% of the nests were located in poplar trees Populus spp. (hybrids of poplars). Nests in villages were located at the height of 5 to 20 meters, and most of them (n = 32, 70%) were over 10 meters high. Outside built-up areas, the height was 3 to 12 meters,

4 512 Grzegorz Orłowski and 70% of them (n = 7) were built below 5 meters. The mean height of nests in village areas was nearly twice that in open farmland (mean ± SD = 11.1 ± 3.7 m in villages vs. 5.7 ± 2.9 m in open areas). This difference was statistically significant (Mann-Whitney test, U = 52.50, Z = 3.80, p < 0.001). Nests in open land were at a distance of 200 to 850 meters from the nearest buildings, the average (± SD) distance being 382 (± 198) m. Fig. 1. Distribution of magpie nests (N=56) in agricultural landscape of the Wrocław Plain. Thick grey line indicates borders of the area (15.8 km 2 ) studied from by Ławniczak (1980) Ryc. 1. Rozmieszczenie gniazd sroki (N=56) w krajobrazie rolniczym Równiny Wrocławskiej. Grubą szarą linią zaznaczono granicę powierzchni (15,8 km 2 ) badanej w latach przez Ławniczak (1980)

5 Magpie Pica pica nest sites in farmland in vicinity of Wrocław city (SW Poland) 513 Table 1. Nest-tree species in agricultural landscape of Wrocław Plain Tabela 1. Drzewa gniazdowe sroki w krajobrazie rolniczym Równiny Wrocławskiej Tree species/gatunek drzewa Number of nests/liczba gniazd Percentage/Udział (%) Poplar Populus sp.* Small-leaved lime Tilia cordata Common ash Fraxinus excelsior Pedunculate oak Quercus robur European alder Alnus glutinosa Black locust Robinia pseudacacia Silver birch Betula pendula Crack willow Salix fragilis Lombardy poplar Populus nigra Italica European white elm Ulmus laevis London plane tree Platanus x acerifolia Apple Malus sp European plum Prunus domestica Mulberry Morus alba Grey willow Salix cinerea Blackthorn Prunus spinosa Unidentified fruit trees Total/Razem *Hybrids of the native black poplar Populus nigra with north-american species *Hybrydy rodzimej topoli czarnej Populus nigra z gatunkami północnoamerykańskimi Discussion and conclusions The data obtained indicated that in the Wrocław Plain, the magpie population is mainly found in village areas. In western Europe (Scotland, Denmark, Germany, Great Britain) in the sixties and eighties in agricultural areas from 40 to 100% of the nests was located in settlements (compiled by Jerzak 1988). Also in the Lubusian Region (NW Poland) the share of nests located in villages was from 76 90% (Jerzak 1988). The total density of magpie nests in the Wrocław Plain, was in the range recorded from other Polish agricultural areas (i.e. from 0.2 to 1.4 pairs/km 2 ) (Dombrowski 1997). Amarginally higher density (1.5 pairs/km 2 ) was found in 1994 on cultivated fields (6.7 km 2 ) situated in the outskirts of Wrocław (Orłowski et al. 2002). On six plots in the farming landscapes around the town of Koszalin there was a large differences in density between village areas and the open agricultural landscape (density from 4.7 to 29.6 pairs/km 2 ), similar to that recorded in the Wrocław Plain. In one of the plots the density was found to be 129 times higher in the village area than in the neighbouring agricultural fields (Górski 1997). The overall density

6 514 Grzegorz Orłowski in village areas of Wrocław Plain (10.1 pairs/km 2 ) is close to results given for urban areas in Poland (compiled by Orłowski et al. 2002). In 1994 in the urban area of south-west part of Wrocław (19.46 km 2 ) the density was found to be 12.6 pairs/km 2 (Orłowski et al. 2002). In the agricultural landscape of the Wrocław Plain, like in urban areas in Poland (Jerzak 1997) the largest percentage of nests was situated on poplar hybrids Populus spp. (21.5% Wrocław Plain vs. 31% Poland) which are characterized by broadly spreading crowns. Also in the south-western part of Wrocław poplar hybrids were the most favoured nesting tree (34.5%) (Orłowski et al. 2002). Up to the present, mid-field magpie populations tended to nest in tussocks of blackthorn and hawthorn along country roads and field margins (Ptaszyk 2000). In spite of the presence of such biotopes in the area studied, only one nest was found in blackthorn. In the Wrocław Plain the mean height of nest sites in villages was close to that reported by Jerzak (1988) for that environment in Poland (12.3 m Poland vs Wrocław Plain). However, in the Wrocław Plain the nests were built slightly higher outside built-up areas compared with data for the rest of Poland (5.7 Wrocław Plain vs. 4.1 Poland). This also influenced the lack of nests in low bushes (blackthorn, hawthorn, bushy willows). Outside town areas as many as 64.1% nests were situated m above the ground, on low willows Salix spp. and blackthorn bushes (Jerzak 1988). Compared to the data from originating from an area of 15.8 km 2 (Ławniczak 1980) situated in the middle of the area studied (Fig. 1), a 2 3-fold decrease in the magpie population was recorded. In the seventies 17.5, 10 and 14.5 magpie pairs breed there, successively; and in winter of 2001/2002 there were 5 nests (this represented a 2 3-fold decrease in density, from to 0.32 prs/km 2 in the respective period). During this period the density remained stable at the former level in villages (Smardzów and Łukaszowice Fig. 1). In western Europe a decrease in magpie populations within agricultural fields has been observed since the 1960s (Cooke 1979, Gregory and Marchant 1995). In the light of the results obtained, and in view of the intensification of agricultural production, one can expect a further withdraw of the magpie from farmland. Most probably that process will further extend to eastern Europe. The magpie, however, contrary to other farmland birds is not a potentially endangered species, as its populations are abundant in urban areas and on the increase in that environment. References Birkhead T.R The Magpies. T&AD Poyser, London. Cooke A.S Population declines of the Magpie Pica pica in Huntingdonshire and other parts of eastern England. Biol. Conserv. 15: Dombrowski A The abundance of breeding populations of magpie Pica pica in different types of agricultural landscape in Poland. Acta Ornithol. 32, 1: Fasola M., Brichetti P Mosaic distribution and breeding habitat of the Hooded Crow Corvus corone cornix and the Magpie Pica pica in Padana Plain (Northern Italy). Avocetta 7:

7 Magpie Pica pica nest sites in farmland in vicinity of Wrocław city (SW Poland) 515 Górski W Distribution and number of Magpie nests and Rook colonies in Pesc (southern Hungary) in Not. Orn. 30: Górski W Urban and rural populations of the magpie Pica pica in the Koszalin region, NW Poland. Acta Ornithol. 32: Gregory R.D., Marchant J.H Population trends of Jays, Magpies, Jackdaws and Carrion Crows in the United Kingdom. Bird Study 43: Jerzak L Distribution and nest sites of Magpie in non-urban habitats in Poland. Not. Orn. 29: Jerzak L Magpie Pica pica nest sites in urban habitats in Poland. Acta Ornithol. 32, 1: Jerzak L Synurbanization of the magpie in the Palearctic. In: Marzluf J.M., Bowman R., Donnelly R. (eds.). Avian ecology and conservation in an urbanizing world. Kluwer Acad. Publishers, p Kondracki J Physical geography of Poland. 6-th edition. PWN, Warszawa. Ławniczak. D Breeding bird communities in different types of agricultural landscapes of Silesia. Ph.D. thesis. Department of Avian Ecology UW, Wrocław. Orłowski G., Martini K., Martini M Number and distribution of the Magpie Pica pica in the south-western part of Wrocław. Ptaki Śląska 14: Ptaszyk J Pica pica (L., 1758) sroka. In: Bednorz J., Kupczyk M., Kuźniak S, Winiecki A. Ptaki Wielkopolski. Monografia faunistyczna. Bogucki Wyd. Nauk., Poznań, p Siriwardena G.M., Baillie S., Buckland S., Fewster R., Marchant J., Wilson J Trends in the abundance of farmland birds: a quantitative comparison of smoothed Common Birds Census indices. J. Appl. Ecol. 35: Tomiałojć L., Stawarczyk T Awifauna Polski. Rozmieszczenie, liczebność i zmiany. PTPP pro Natura. Wrocław.