Breeding densities and habitat selection of the Common Swift (Apus apus) in the city of Wrocław

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1 Sylvia 44 / 2008 Breeding densities and habitat selection of the Common Swift (Apus apus) in the city of Wrocław Hnízdní hustota a výběr hnízdního prostředí rorýse obecného (Apus apus) ve Vratislavi Grzegorz Kopij 1,2 1 Institute of Natural Sciences, Wrocław University of Environmental & Life Sciences Pl. Grunwaldzki 24a, Wrocław, Poland 2 Department of Zoology and Ecology, Wrocław University of Environmental and Life Sciences, ul. Kożuchowska 5b, Wrocław, Poland; grzegorz.kopij@up.wroc.pl Kopij G. 2008: Breeding densities and habitat selection of the Common Swift (Apus apus) in the city of Wrocław. Sylvia 44: In July 2006, a method developed by Falkenberger et al. (2004) was used to estimate Common Swift breeding densities in 17 plots (with the total area of 680 ha) in the city of Wrocław, SW Poland. In the study plots, breeding densities ranged from 0 to 153 pairs per 10 ha; the highest ( pairs / 10 ha) were found in the oldest parts of the city, while the lowest (0 6 pairs / 10 ha) in villages situated within the administrative boundaries of the city. The entire breeding population in Wrocław (292 km 2 ) is estimated at 6,430 pairs. The average breeding density in the city is therefore 2.2 pairs / 10 ha, while the ecological density (only built up areas considered) reaches 7.8 pairs / 10 ha. V červenci 2006 jsem pomocí metody Falkenbergera et al. (2004) odhadoval hnízdní hustotu rorýse obecného (Apus apus) na 17 plochách (o celkové rozloze 680 ha) ve Vratislavi (Wrocław) v jihozápadním Polsku. Hnízdní hustota se na zkoumaných plochách pohybovala od 0 do 153 párů na 10 ha; nejvyšší ( párů / 10 ha) byla v nejstarších částech města, nejnižší (0 6 párů / 10 ha) ve vesnicích zahrnutých v administrativních hranicích města. Hnízdní populace v celém městě (292 km 2 ) byla odhadnuta na párů. Průměrná hnízdní hustota činila tedy 2,2 párů / 10 ha, zatímco ekologická hustota (zahrnuty pouze zastavěné oblasti) 7,8 párů / 10 ha. Keywords: Apus apus, breeding density, Common Swift, habitat, urban ornithology INTRODUCTION The Common Swift (Apus apus) is widespread throughout Europe, with numbers reaching more than 6,700,000 pairs (BirdLife International 2005). Its population in most European countries is regarded as stable (Bauer & Berthold 1996, BirdLife International 2005). There is, however, a lack of reliable quantitative estimates of its population for the whole countries as well as for particular cities (Glutz von Blotzheim 1980, Cramp 1985, but see Antonov & Atanasova 2002). This is partly because no appropriate swift census method was available for a long time. Based on seasonal and daily activity of the Common Swift and its so called 37

2 Kopij G. / Common Swift breeding densities screaming display, Falkenberger et al. (2004) have recently proposed a method enabling fairly accurate estimate of breeding density of the species in Berlin. The major advantage of this method is a relatively simple field procedure and that it is not much time-consuming. In the present paper, I used the method to estimate population density of the Common Swift in major urban habitats in one of the biggest Polish cities. Based on the results, I also tried to estimate the total number of breeding pairs of the species in the whole city. METHODS The study was carried out in Wrocław, the capital of Silesia, SW Poland. In 2004, the city was inhabited by ca. 666,000 resident citizens. Its area within the administrative boundaries is 292 km 2, with builtup areas covering only approximately one third. In 2002, the structure of land use within the administrative boundaries of Wrocław was as follows: 29% builtup areas, 10% roads and railways, 43% arable fields, 6% woodlands and other areas with trees, 4% wetlands, 8% other areas (Herasimowicz 2002). The central part of the city is a densely built-up area founded as early as in the 13 th century, but most of the today s buildings come from the 18 th 20 th centuries. Buildings in other parts of the city were constructed mainly in the 20 th century, with some dating back to the 19 th century. For the purpose of this study 17 plots were randomly selected to represent all urban microhabitats in the city (Fig. 1). city boundaries Rivers main roads built-up-areas densely built-up-areas Fig. 1. Map of the city of Wrocław showing the position of 17 study plots (cf. Table 1). Obr. 1. Mapa Vratislavi s čísly sledovaných ploch (srov. tab. 1). 38

3 Sylvia 44 / 2008 Table 1. Characteristics of study plots (height of the buildings is given as the number of stories) cf. Fig. 1. Tab. 1. Charakteristiky studijních ploch (výška budov je vyjádřena jako počet poschodí) srov. obr. 1. High vysoká, average průměrná, low nízká No. study plot boundaries of the study plot buildings surface inds./ 10 ha extrapolation č. studijní plocha hranice studijní plochy budovy plocha [ha] ex./10 ha extrapolace age height density surface inds./10 ha stáří výška hustota plocha [ha] ex./10 ha (stol., roky) old densely built-up areas / stará hustá zástavba 1 Ostrów Tumski Wyszyńskiego-Hlonda-Kanonia-Piasek th cent. 3 and 10 high Old Town, East Kaz. W.-Modrzejew.-Św. Ducha-Szewska th cent. 5 high Old Town, West Kazimierza W.-Nowy Świat-Szewska th cent. 5 and 10 high block buildings / sídliště 4 Ołbin Sienkiewicza-JN-Żeromskiego th cent. 5 high Plac Grunwaldzki Skłodowskiej-Pl. Grunwald.-Wyspiańsk and 10 high Gaj, northern part Borowska-Kamienna-Widna-AK 1980 s 5 average Gaj, southern part Borowska-AK-Świeradowska-Bardzka 1980 s 10 average residential areas / vilové čtvrti 8 Biskupin Pautscha-Olszewsk.-Bartoszow.-Gierymsk average Sępolno Mickiewicza-9.V-Dembow.-M. Cassino average Zalesie Różyck.-Paderewsk.-Wieniawsk.-Chopina 1920/30, 1960/70 2 average Zacisze Gr. Szczytnicka-Czackiego-Śniadeckiego 1920/30, 1960/70 2 average Strachocin Strachocińska-Narciarska- railway average industrial areas / průmyslové oblasti 13 ul. Krakowska AK-Wilcza-Młoda-Chudoby-railway 1880 s, 1990 s 2 low villages / vsi 14 Opatowice Opatowicka 1 st half 20 th cent. 1 low Swojczyce Miłoszycka-Swojczycka-Ceglana 1 st half 20 th cent. 1 average Ratyń Gromadzka-Szkolna 1 st half 20 th cent. 1 average Rędzin Wędkarzy-Piłkarzy-Łyżwiarzy 1 st half 20 th cent. 1 low in total / celkem

4 Kopij G. / Common Swift breeding densities The average surface of the study plots was 40 ha, ranging from 15 to 95 ha. Their total surface was 680 ha. Based on the density of buildings, their age, height and amount of green areas, these microhabitats were grouped into five categories: old densely built-up areas, block buildings, residential areas, industrial areas and villages. Block buildings and residential areas were further divided into new and old ones (Table 1). The method developed by Falkenberger et al. (2004) was used in this study. The birds were counted from July 21 till July 31, Two counts were carried out in each plot, the first one in the evening, i.e. between 7:30 and 9:30 pm, and the second one, a week later, in the morning, i.e. between 6:30 and 8:30 am. During the counts, special attention was paid to birds performing the so-called screaming display. Birds in such display fly around buildings in which their breeding colonies are established. When such buildings were localized, all birds performing the screaming display, as well as those which were flying in close vicinity (usually above) of these buildings, were counted for 2 4 times. The maximum number of individuals recorded in any of these counts (either in the evening or in the morning) was taken as the best indication of the number of pairs nesting in these buildings (cf. Falkenberger et al. 2004). RESULTS AND DISCUSSION In the particular study plots, breeding densities ranged from 0 to pairs per 10 ha (Table 1). The average density per plot was pairs (SD = 122.6; n = 17) and when the plots with the absence of Common Swifts were excluded (n = 3), the average density per plot was pairs (SD = 122.0; n = 14). The highest densities ( pairs / 10 ha) were recorded in the oldest parts of the city, while the lowest (0 6 pairs / 10 ha) in villages situated within the administrative boundaries of the city. There was almost two times higher density of breeding Common Swifts in areas with old than in areas with new block buildings. In the latter areas, similar densities were recorded in plots with 5-storey and in plots with 11-storey blocks (Table 1). Similarly in residential areas, much higher density of breeding swifts was recorded in plots with older than in plots with younger buildings (Table 1). Common Swifts nested in rather low densities in industrial areas. In villages, they nested only where suitable old and relatively tall buildings (often with brick walls) were present. In areas with block buildings, House Martins (Delichon urbica) were often recorded to breed colonially in an association with Common Swifts (own unpubl. data). However, no such cases were recorded in the old densely built-up areas. The much higher densities of Common Swifts in the densely built-up areas may be explained simply by the higher abundance of available nest holes compared to block-building areas. Another possible factor could be the lack of competition with House Martins in the old densely built-up areas. Preference of the Common Swift for old and tall buildings has also been shown in Berlin (Falkenberger et al. 2004) and Warsaw (Luniak et al. 2001, Nowicki 2001). The birds usually locate their nests in air-holes, under eaves and under gutters (Cramp 1985) and these structures are available in most cases in older and taller buildings. Most of the Common Swift colonies were composed of pairs. The largest colonies recorded were situated in monumental medieval churches, namely in the Most Holy Mary s the Virgin (c. 200 pairs), the Holy Cross (c. 140 pairs), 40

5 Sylvia 44 / 2008 the Dominican s (c. 140 pairs) and St. Elizabeth s (c. 60 pairs). However, only small swift colonies were found in St. Magdalene s Church and in St. John the Baptist Cathedral, which rank among the oldest and biggest churches in Wrocław. Towers of the St. John the Baptist Cathedral were thoroughly renovated in , while in St. Magdalene s Church roofing tiles were exchanged several years ago. By an extrapolation of these results, the entire breeding population in Wrocław (292 km 2 ) is estimated at 6,430 pairs. The average breeding density in the city is therefore 2.2 pairs / 10 ha. The ecological density (only built up areas considered) is much higher, reaching 7.8 pairs / 10 ha. However, these figures should only be taken as very rough estimates because of the inherently high spatial variance in the availability of suitable nesting places in swifts, rendering extrapolation risky. In 1990, breeding population of the Common Swift in Poland was estimated at 100, ,000 pairs (BirdLife International 2005). The huge range indicates that this estimate is, by no means, precise and accurate. In Berlin, 21,000 pairs (2.4 pairs per 10 ha for the entire city or 5.8 pairs / 10 ha as the ecological density) were counted using the same method (Falkenberger et al. 2004). Common Swifts thus seem to breed in quite similar densities in Berlin and Wrocław. However, the density in Warsaw was much lower; the crude density was estimated at pairs / 10 ha, while ecological densities at pairs / 10 ha (Luniak et al. 2001). Also ecological densities of Common Swifts breeding in smaller towns appear to be much lower than in Wrocław, ranging from 0.8 to 2.5 pairs per 10 ha (Table 2). Most Common Swift colonies are composed of no more than pairs (Cramp 1985, Antonov & Atanasova 2002) and only rarely up to 100 pairs (Glutz von Blotzheim 1980). In Wrocław, there were at least three such huge colonies. This may suggest that there is an exceptionally high concentration of Common Swifts in Wrocław, possibly one of the highest in Central Europe. SOUHRN V červenci 2006 byla pomocí metodiky zavedené Falkenbergerem et al. (2004) odhadována hnízdní hustota rorýse obecného (Apus apus) ve Vratislavi Table 2. Numbers of breeding pairs of the Common Swift in some Polish towns and cities. Surface of the built-up area is given in brackets. Tab. 2. Počet hnízdních párů rorýse obecného v některých polských městech. Rozloha zastavěných ploch je uvedena v závorkách. town/city surface [km 2 ] No. of pairs period source město rozloha [km 2 ] počet párů období zdroj Wrocław 292 (89) this study / tato studie Warszawa 494 (177.8) Luniak et al Leszno 31.9 (12.8) Kuźniak 1996 Gorzów Wlkp (15) Jermaczek et al Jasło Stój & Dynkowski 2002 Sulechów Czwałga 1992 Korfantów G. Kopij, unpubl. Poniec Lorek

6 Kopij G. / Common Swift breeding densities (Wrocław) v jihozápadním Polsku. Tato metoda je velmi jednoduchá, časově nenáročná a umožňuje poměrně přesný odhad hnízdní hustoty. Celkem bylo vybráno 17 studijních ploch o celkové rozloze 680 ha, které reprezentovaly hlavní typy urbánních mikrohabitatů (tab. 1, obr. 1). Hnízdní hustota se na zkoumaných plochách pohybovala od 0 do 153 párů na 10 ha (tab. 1); nejvyšší ( párů / 10 ha) byla v nejstarších částech města, zatímco nejnižší (0 6 párů / 10 ha) ve vesnicích zahrnutých v administrativních hranicích města. Většina kolonií čítala párů, nejpočetnější kolonie byly zjištěny ve věžích velkých středověkých kostelů (ve třech případech > 100 párů). Hnízdní populace v celém městě (292 km 2 ) byla extrapolací odhadnuta na párů. Průměrná hnízdní hustota je tedy 2,2 párů / 10 ha, zatímco ekologická hustota (zahrnuty pouze zastavěné oblasti) 7,8 párů / 10 ha. Vzhledem k velké prostorové variabilitě vhodných hnízdních možností v rámci města se ale jedná o hrubý odhad. Přesto tato metoda ukázala, že ve Vratislavi rorýsi obecní hnízdí velmi početně a dosahují tak pravděpodobně jedné z nejvyšších hnízdních hustot ve střední Evropě (srov. též tab. 2). LITERATURE Antonov A. & Atanasova D. 2002: Cohabitation and nest-site selection of Common Swift (Apus apus) and Pallid Swift (A. pallidus). Vogelwarte 41: Bauer H.-G. & Berthold P. 1996: Die Brutvögel Mitteleuropas. Bestand und Gefährdung. AULA-Verlag, Wiesbaden. BirdLife International 2005: Birds in Europe: Population Estimates, Trends and Conservation Status. BirdLife International, Cambridge, UK. Cramp S. (ed.) 1985: Birds of the Western Palearctic. Vol. 4. Oxford: Oxford Univ. Press. Czwałga T. 1992: Awifauna lęgowa miasta Sulechowa w latach Lub. Prz. przyr. 3(2/3): Falkenberger M., Böhner J., Salinger S., Schulz W., Strehlow H., Witt K. & Tigges U. 2004: Mauersegler (Apus apus) in Berlin: Lebensraumtypische Dichten und Bestand Berl. ornithol. Ber. 14: Glutz von Blotzheim U. N. (ed) 1980: Die Vögel Mitteleuropas. Bd. 9. AULA-Verlag, Wiesbaden. Harasimowicz J (ed.): Encyklopedia Wrocławia. Wyd. Dolnośląskie, Wrocław. Jermaczek A., Czwałga T., Jermaczek D., Nowak A., Stańko R., Schneider G. & Żegliński G. 1992: Ptaki lęgowe miasta Gorzowa w roku Lub. Prz. przyr. 3(2/3): Kuźniak S. 1996: Atlas ptaków lęgowych Leszna. Pr. Zakł. Biol. Ekol. Ptaków UAM 6: Lorek G. 1986: Awifauna lęgowa miasta Ponieca. Lub. Przegl. przyr. 3(4): Luniak M., Kozłowski P., Nowicki J. & Plit J. 2001: Ptaki Warszawy Warszawa: MiIZ PAN. Nowicki W. 2001: Ptaki śródmieścia Warszawy. Warszawa: MiIZ PAN. Stój M. & Dynkowski J. 2002: Ptaki Jasła: liczebność, rozmieszczenie, ochrona. Poznań: Bogucki Wydawnictwo Naukowe. Došlo 19. prosince 2007, přijato 25. února Received December 19, 2007; accepted February 25, Editor: P. Procházka 42