ISSN 2336-3193 Acta Mus. Siles. Sci. Natur., 69: 175-180, 2020 DOI: 10.2478/cszma-2020-0013 Published: online 1 July 2020, print July 2020 Distribution and numbers of waterbird species breeding in the city of Wrocław Grzegorz Kopij Distribution and numbers of waterbird species breeding in the city of Wrocław. – Acta Mus. Siles. Sci. Natur. 69: 175-180, 2020. Abstract: During the years 2003-2010, the numbers of pairs of waterbird species breeding in the city of Wrocław (293 km2) were assessed. The city is situated in Odra valley, where four smaller rivers join it. The city abandons in oxbows, gravel and sand, and clay pits and other water bodies. In total, 20 waterbird species were recorded as breeding in Wrocław. The most common were Anas platyrhynchos (145-212 pairs), and Fulica atra (70-104 pairs). Relatively common were also the Gallinula chloropus (28-37 pairs), Rallus aquaticus (9-25 pairs) and Cygnus olor (9-11 pairs). For each remaining species less than 10 pairs were recorded. Among rare species, the following were recorded as breeding in Wrocław: Grus grus, Mergus merganser, and Porzana porzana. In the few recent decades, the increase in the number of breeding pairs was recorded for Anas platyrhynchos and Cygnus olor; while a parallel decrease was recorded for Fulica atra, Gallunula chloropus, Chroicocephalus ridibudnus, and Tachybaptus ruficollis. Species such as the Aythya fuligula, Aythya ferrina, grebes, gulls and terns avoid the city. Some of them even ceased to breed (Anas quarquedula, Anas clypeata and Botaurus stellaris). The city plays an important role in protecting water bird species such as Grus grus, Cygnus olor, Porzana porzana and Alcedo atthis. Key words: urban ornithology, waterbirds, censuses, nature conservation. Introduction Waterbirds are very attractive group of urban fauna, both during the breeding season, on autumn and spring passage, as well as during the winter (Jakubiec 1985; Kalcey, Rheinwald 2005). This group, highly prized as game birds, includes large and colourful species, with very interesting behavior. Many of them are regarded as key umbrella or charismatic species in nature conservation. In this paper, an attempt is taken to assess their numbers and distribution in the largest city in SW Poland. It constitutes a further contribution to the knowledge of birds in the entire area of the city of Wroclaw (Kopij 2008a, 2016a, 2016b, 2017a, 2017b, 2018, Kopij et al. 2009, Kopij & Wawrzyniak 2015). Studies on the numbers and distribution of waterbird species in larger cities in Poland have hitherto been undertaken only in Wrocław (Luniak et al. 2001) and in Łódź (Janiszewski et al. 2009). Due to a large number of ponds, dams, gavel and clay pits, canals and rivers, Wrocław constitutes an environment very attractive to waterbirds. The aim of this work is to investigate numbers and distribution of waterbird species breeding in this city. Study area The city of Wrocław, a capital of Lower Silesia, is situated in the valley of a large river, Odra, where four smaller rivers (rivers of II order: Oława, Ślęża, Bystrzyca and Widawa) join it. The total surface area of Wrocław (within its administrative bounders) is 293 km2. In 2004, human population reached 640 000. The arable grounds comprised 44.8% of the total surface area, forests and other timbered/afforested areas – 5.6%, built-up areas – 18.7%, roads -9.8%, gardens – 3.7%, recreational areas – 6.1%, wastelands – 1.3%. Wetlands and meadows comprise 6.6%, while rivers, canals and all sorts of water bodies – 3.4% of the total surface area (Smolnicki & Szykasiuk 2002). 175 The length of the Odra River within the city Wrocław is 27 km (80 km if all canals are included), Oławy – 19.5 km, Ślęży – 15 km, Bystrzycy – 15 km, and Widawy – 19.5 km. Together - 96 km. Kasina, Łękawica, Toczek, Brochówka, Piskorna comprise smaller river networks. Although Odra is entirely canalized within the city of Wrocław, it forms numerous islands (all under management), meanders, bays, mill-dams etc. In some stretches, banks of the river are covered with narrow belts of reeds and other emergent water plants. Odra leaves the city at 108 m a.s.l. In 1976, there were 326 water bodies in Wrocław, but only 211 of them remained in 1996, and still less remained in 2003-2010. Many of the water bodies are remnants of Odra, Oława, Bystrzyca and Widawa oxbows (e.g. Czarna Woda between Zalesie and Zacisze, ponds in Botanic Garden, Szczytnicki Park, Swojczycki Park and Japanese Garden). There are numerous clay pits scattered all over the city, but these are especially numerous in Fabryczna district (e.g. Żerniki, Muchobór Wielki, Stabłowice, Swojczyce, Maślice Małe). Some industry retention dams were built in Sołtysowice and Klecinia. There are also numerous sewage dams near Rędziny, between Odra and Widawa, and extensive polders with numerous ponds and canals near Świątniki, between Odra and Oława. However, there are no larger waterbodies, such as lakes and water reservoirs. The climate of Wrocław is temperate, slightly warmer than in the neighbouring areas. The mean annual temperature is 9.7˚C, the mean temperature of coldest month (January): -0.5˚C, and the hottest (July): +19.9˚C. The mean annual precipitation – 548 mm; mean humidity – 76%. On average, there are 158 days with rain/snow per year and 1670 hours of sunny weather per year. Snow cover retains for 35 days per year (Bryś & Bryś 2014). Methods Waterbird species are defined as those which are associated with water, both as a foraging and nesting place. Therefore, the following taxonomic groups are included: Podicipediformes, Anseriformes, Charadriiformes and Rallidae. Passerine species nesting in water vegetation are excluded, i.e. Emberiza schoeniclus, Locustella luscinioides, Acrocephalus arundinaceus, Acrocephalus scirpaceus and Luscinia svecica. Excluded are also Circus aeruginosus and Ciconia ciconia. All those species were subjects of other publications (Kopij 2016a, 2017a, 2018, Orłowski et al. 2008). All water and wetland habitats within the city of Wrocław (Fig. 1) were surveyed at least twice: in April/May and in June/July. The whole area of the city was covered during the years 2003-2010. These habitats were surveyed more thoroughly and systematically in the inner part of the city (Kopij 2004, 2005, 2007, 2008, 2010, 2014a, 2014b, 2014c, 2016c). In the case of ducks (Anatidae), Cygnus olor, Fulica atra, Galinulla chloropus, grebes (Podicipedidae) and Alcedo atthis, only pairs with nest containing eggs or chicks or adults brooding chicks were regarded as a breeding pair. In the case of Grus grus, Porzana porzana, Charadrius dubius, Actitis hypoleucos and Motacilla cinerea, also individuals performing breeding or territorial behaviour were regarded as breeding pairs. Results and discussion During the years 2003-2010, a total of 20 breeding waterbird species were recorded in the city of Wrocław (Table 1, 2; Fig. 1-10). As expected, the most numerous species was the Mallard Anas platyrhynchos and Coot Fulica atra (Fig. 8). Together they comprised 70- 73% of all breeding pairs of the waterbird species. Relatively numerous were also the Moorhen Gallinula chloropus and Water Rail Rallus aquaticus (Fig. 3). The remaining species nested in a density lower than 10 pairs each in the whole city (Table 1). Waterbird species such as Water Rail, Little Crake Porzana parva, Spotted Crake Porzana porzana could have been underestimated in this study, as they are elusive and active mainly in the night. They are best detected by broadcasting their calls in their potential habitats, which was, however, not carried out in Wrocław. The areas with sewage dams near Rędzin between Odra and Widawa, polders near Świątniki between Odra and Oława and clay pits in Fabryczna district were the most often occupied breeding sites of the waterbirds (Fig. 1-10). Contrary to expectations, most waterbird species were not recorded on Odra River, because the river in entirely canalized with only narrow rows of emergent water vegetation. The Mute Swan was recorded for the first time as a breeding bird in Wrocław in 1984 (Lontkowski et al. 1988). In the following years (1985-87), single pairs nested also in Strachociński Pond and Zakrzów (Dyrcz et al. 1991). During the years 2003-2010, few pairs 176 regularly nested in a few sites in various parts of the city (Fig. 7). Table 1. Number of breeding pairs of water birds in Wrocław (this study), Warsaw (Luniak et al. 2001) and Łódź (Janiszewski et al. 2009). Species Wrocław (293 km2) Warszawa (494 km2) Łódź (293 km2) N pairs/10 km2 N pairs/10 km2 N pairs/10 km2 Cygnus olor 9-11 0.31-0.38 4-7 0.14 2 0.07 Fulica atra 70-104 2.39-3.55 150-200 3.04-4.05 36-50 1.23-1.71 Galinulla chloropus 28-37 0.96-1.26 40-60 0.81-1.21 9-11 0.31 Rallus aquaticus 9-25 0.31-0.85 15-40 0.30-0.81 1 0.03 Podiceps cristatus 6 0.20 10-20 0.20-0.40 0 0.00 Tachybaptus ruficollis 5 0.17 20-30 0.40-0.61 6-9 0.20-0.31 Alcedo atthis 6 0.20 10-15 0.20-0.30 0 0.00 Grus grus 2 0.07 0 0.00 0 0.00 Porzana parva 3 0.10 <5 0.10 0 0.00 Aythya fuligula 2 0.07 5-10 0.10 16-20 0.55-0.68 Aythya ferrina 6 0.20 3-5 0.06 6 0.20 Mergus merganser 2 0.07 5-8 0.10 0 0.00 Anas platyrhynchos 145-212 4.95-7.42 400-600 8.10-12.15 140-200 4.78-6.83 Charadrius dubius 7 0.24 12-20 0.24-0.40 5-6 0.17-0.20 Actitis hypoleucos 1 0.03 5 0.10 0 0.00 Motacilla cinerea 1 0.03 0 0.00 0 0.00 Chroicocephalus ridibundus 2 0.07 200-350 4.05-7.09 0 0.00 Larus canus 1 0.03 10-20 0.20-0.40 0 0.00 Table 2.