Breeding Densities of Woodpeckers (Picinae) in the Inner and Outer Zones of a Central European City

SYLVIA 53 / 2017

Breeding densities of woodpeckers (Picinae) in the inner and outer zones of a Central European city

Hnízdní hustoty „datlů“ (Picinae) ve vnitřní a vnější zóně středoevropského města

Grzegorz Kopij

Department of Vertebrate Ecology, Wrocław University of Environment & Life Sciences, Kożuchowska 5 b, 51-631 Wrocław, Poland

Kopij G. 2017: Breeding densities of woodpeckers (Picinae) in the inner and outer zones of a Central European city. Sylvia 53: 41–57.

During the years 2003–2010, woodpecker territories were mapped within the administrative boundaries of the Wroclaw city, SW Poland. The total area of the city is 293 km 2, including 32 km 2 of wooded areas dominated by old oaks (13 forests, 44 parks and many alleys and other scattered tree vegetation). In the present study, two zones of the city were distinguished – the inner (more than 50% of built-up areas; ca. 1/3 of the whole study area) and the outer zone (mostly open and forested areas; ca. 2/3 of the whole study area). Seven woodpecker species were recorded with the following ecological densities (pairs per 1,000 ha of wooded areas): Dendrocopos major – 62.5, Picus viridis – 13.8, Dendrocoptes medius – 12.5, Dryobates minor – 11.6, Dryocopus martius – 6.6, Picus canus – 4.4, and Dendrocopos syriacus – 0.6. Population densities of the typical forest woodpeckers, i.e. Dryocopus martius, Dendrocopos major, and Dendrocoptes medius , were higher in the outer than in the inner zone of the city, while population densities of the forest-steppe species, i.e. Picus canus and Picus viridis , were higher in the inner than in the outer zone. Overall population densities of all woodpecker species were considerably higher in wooded areas in the outer than in the inner zone of the city, namely 114.7 versus 103.6 pairs per 1,000 ha of wooded areas.

V letech 2003–2010 jsem mapoval teritoria „datlů“ v katastru města Vratislavi, jz. Polsko. Celková rozloha studované oblasti je 293 km 2, včetně 32 km 2 porostů dřevin s převažujícími starými duby (13 lesů, 44 parků a mnoho alejí a dalších prvků rozptýlené zeleně). Město bylo rozděleno na vnitřní (více než 50 % zastavěných ploch; cca 1/3 celkové studijní plochy) a vnější zónu (převažující otevřené a zalesněné plochy; cca 2/3 celkové studijní plochy). Bylo zaznamenáno sedm druhů „datlů“ s následujícími ekologickými populačními hustotami (páry na 1 000 ha porostů dřevin): Dendrocopos major – 62,5, Picus viridis – 13,8, Dendrocoptes medius – 12,5, Dryobates minor – 11,6, Dryocopus martius – 6,6, Picus canus – 4,4 a Dendrocopos syriacus – 0,6. Populační hustoty typických lesních druhů ( Dryocopus martius, Dendrocopos major, Dendrocoptes medius ) byly vyšší ve vnější zóně města, zatímco populační hustoty lesostepních druhů ( Picus canus, Picus viridis) byly vyšší ve vnitřní zóně města. Celkové populační hustoty všech druhů dohromady byly vyšší ve vnější zóně města, konkrétně 114,7 oproti 103,6 párům na 1 000 ha porostů dřevin.

Keywords: communal forest, park, territory mapping, urban ecology, Wrocław.

41 Kopij G. / Woodpeckers in the inner and outer zones of a city

INTRODUCTION 2007, Dunn & Weston 2008, Luniak 2017) have recorded most of the woodpecker Woodpeckers (subfamily Picinae) are species in urban parks and forests (even regarded as good indicators of environ- in the city centres). The Great Spotted mental quality (Morrison & Chapman Woodpecker ( Dendrocopos major ), 2005, Myczko et al. 2014). Most species Lesser Spotted Woodpecker ( Dryobates belonging to this group are associated minor ), and Green Woodpecker ( Picus with old tree stands of deciduous or viridis ) are usually considered common, mixed forests. In Central Europe, such while the remaining species are rare habitats have been greatly reduced and and inhabit rather wooded areas in the fragmented. The Birds Directive (79/409/ outer city zones (Yankov 1992, Fuller et EEC) adopted by the E.U. Member States al. 1994, Luniak et al. 2001, Fuchs et al. therefore ensures the protection of most 2002, Hewlett 2002, Otto & Witt 2002, woodpecker species. It is the case of Kalyakin & Volzit 2006, Nowakowski the Black Woodpecker ( Dryocopus mar - et al. 2006, Fraissinet & Dinetti 2007, tius), Grey-headed Woodpecker ( Picus Weiserbs & Jacob 2007, Vránová et al. canus ), Middle Spotted Woodpecker 2007, Czyż 2008, Janiszewski et al. 2009, (Dendrocoptes medius ), White-backed Schlemmer et al. 2013). A few of these Woodpecker ( Dendrocopos leucotos ), atlases have also attempted to estimate and Syrian Woodpecker ( Dendrocopos population densities over the whole city. syriacus). However, due to the conserva- Among larger Central European cities tion of woodland reserves, increasing (with human population of more than the level of forest coverage, and possi- 500,000), such estimates are available bly also due to climate change (milder only for Warsaw (Luniak et al. 2001), Łódź winters), populations of woodpecker (Janiszewski et al. 2009), Berlin (Otto & species have grown in many European Witt 2002), and Hamburg (Mitschke & countries in recent decades (Mikusiński Baumung 2001). 1995, Tomiałojć & Stawarczyk 2003, del Although a considerable body of lit- Hoyo et al. 2014, IUCN 2017). erature exists on the woodpecker habi- However, stands of old trees have sur- tat selection and population densities vived also in cities, either in the form of in forests and urban parks (e.g., Glutz parks in centres or as communal forests von Blotzheim & Bauer 1994, Bauer & on the peripheries. In general, parks and Berthold 1997), most of these studies communal forests have been regarded were carried out in habitat plots smaller as suboptimal, or even marginal habitas than 30 ha, appropriate to estimate densi- for most woodpecker species, because ties of only some very common passerine their vegetation structure is usually sim- species. Such plots are not adequate for plified and the patch sizes may be too the estimation of woodpecker density, as small to enable the birds to establish most of them hold territories larger than territories (Salvati et al. 2001, Myczko those study plots (Glutz von Blotzheim et al. 2014). However, some observa- & Bauer 1994, Kosiński & Kempa 2007). tions undertaken in recent few decades Population studies on woodpeckers on suggest that such habitats may play an larger plots (100–1,000 ha) are much less important role as refuges for species common (e.g., Kosiński & Kempa 2007, associated with old trees (Kopij 2010, Kopij & Hołga 2008), and there are only 2014a, Kopij & Hołga 2008). Numerous few such studies conducted on very large urban bird atlases (Fraissinet & Dinetti plots (>10,000 ha; e.g., Tjernberg et al.

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1993, Kopij 2011). There is a negative re- by sport fields, and 1.3% by wastelands. lationship between population densities Marshlands and meadows comprise al- and the size of the study area (Gaston et together 6.6% (Smolnicki & Szykasiuk al. 1999). Small study plots reveal higher 2002). densities, while much lower densities are Forests in this study are areas used characteristic for large areas (cf. Glutz von mainly for wood production and almost Blotzheim & Bauer 1994). This is partly entirely covered by trees. Tree stands because population densities are often are composed of indigenous species overestimated in small study areas, while and the undergrowth is relatively well- the lower densities in larger areas may developed. Most of the 13 forests in partly be a result of underestimation, as Wrocław (all of them were surveyed) are it may be more difficult to detect birds in dominated by Tilio-Carpinetum stands. large areas. They range in size from 10 to 680 ha The aim of this study was to estimate (median = 175.8 ha) and their total area is breeding densities of woodpecker spe- 2,286 ha. Only two forests (Mokrzański, cies in urban area, where old trees are Rędziński) are dominated by pines relatively well-preserved in parks and (Pinus sylvestris ). In most forests, the urban woods. For each species, popula- age of the canopy trees ranges between tion densities were estimated separately 50 and 100 years. Only in the Leśnicki for the inner and outer zones of the city. and Kosmonautów forests, most trees Unlike in most other studies on wood- are younger than 40 years. Only two peckers’ population density, the pre- smaller forests (Kuźnicki – 9.4 ha, and sented density estimates were derived Rakowiecki – 22.4 ha) were situated in from a large area. the inner zone, while all the other forests were in the outer zone (see below for zone definition). METHODS Parks are semi-open areas composed Study area of timbered and open places with mown The city of Wrocław (SW Poland) is grass, playgrounds, sparse buildings and situated in the large Oder valley, where other man-made structures (e.g., picnic four other smaller rivers (Oława, Ślęża, tables, fountains, monuments, water bod- Bystrzyca and Widawa) join the Oder riv- ies). In comparison with forests, parks er. The climate of Wrocław is temperate, also have a much reduced undergrowth. slightly warmer than that of the neigh- Tree stands, as well as undergrowth, are bouring areas. The mean annual tem- often mixed with exotic species. Parks perature is 9.7˚C. Mean annual precipita- are set aside mainly for recreation, being tion is 548 mm. The snow cover lasts on situated in a close proximity to human average 35 days per year (Smolnicki & settlements. Human pressure is, there- Szykasiuk 2002, Bryś & Bryś 2010). fore, much higher here than in the for- The city within its administrative ests. In Wrocław, there are 44 parks rang- boundaries has an area of 293 km 2 and ing in size from 2 to 120 ha (median = the human population of 637,075 as 17.8 ha), and their total area is 781 ha. Like of 2016. Arable land comprises 44.8% forests, most parks in Wrocław are also of the total area, whereas 5.6% is cov- dominated by Tilio-Carpinetum stands. ered by forests and other wooded areas, In a few parks (Tysiąclecia, Grabiszyński, 3.4% by water, 9.8% by roads, 18.7% by and Skowroni/Andersa), the stands of built-up areas, 3.7% by gardens, 6.1% mixed broadleaved and coniferous trees

43 Kopij G. / Woodpeckers in the inner and outer zones of a city predominate. In all parks, old (age >100 up, open and wooded areas. In the inner years) trees make up more than 50% of zone (ca. 1/3 of the total study area), the tree stand. Only in the Tysiąclecia more than 50% of the area is occupied by park, the trees are 10–20 years old. Four densely built-up areas, while in the outer small (>10 ha) and two larger parks zone (ca. 2/3 of the study area) mostly (Lesicki – 21 ha, Złotnicki – 20 ha) are by open and wooded areas. In the outer located in the outer zone, while all the zone, wooded areas (forests, parks and others are in the inner zone of the city. other wooded areas) cover altogether Other small wooded areas, such as tree 2,380 ha, in the inner part 820 ha. clumps, avenues and hedgerows, are scattered all over the city, but are especially Territory mapping common in the south-eastern part. The A simplified version of the territory map- total area of these habitats is 133 ha. ping method (Bibby et al. 2012) was Two zones were distinguished in the used. I mapped territories of woodpeck- city: inner and outer (Fig. 1). These zones ers associated with forests, parks and differ in the proportion of densely built- other wooded areas as their breeding and feeding habitats. All such habitats within the administrative boundaries of Wrocław were surveyed four times during the breeding season. The first survey was carried out in April, second in May, third in June and fourth in July. The July survey was focused mainly on the Syrian Woodpecker, which starts to breed later in the breeding season than the other woodpecker species (Glutz von Blotzheim & Bauer 1994). Different parts of the city (2,000–5,000 ha) were surveyed in different years Fig. 1. The study area in the city of Wroclaw. (Fig. 1). Some of them (200–2,000 ha) Black solid line – a border between the inner were covered by Kopij (2004, 2005, 2007, and outer zones of the city; black dashed 2008, 2010, 2014a,b,c, 2016 a) an d Kopij & line – borders of the particular study plots Hołga (2008). All parts of the city, and (a year of survey is given). Colour filling: all wooded habitats were covered within black – railways; purple – industry areas; the period from 2003 to 2010. red – densely built-up areas (city centre); orange – sparsely built-up areas; dark green Each visually or acoustically recorded – forests; light green – parks; bluish green – woodpecker individual was plotted on grasslands; yellow – arable grounds. the map 1 : 10,000. Special attention was Obr. 1. Studovaná oblast ve městě Vratislavi. paid to simultaneously calling and drum- Černá souvislá čára – hranice mezi vnitř- ming birds and those performing other ní a vnější zónou města; černá přerušova- territorial and/or breeding behaviour. ná čára – hranice dílčích studijních ploch Sex was determined if possible. At least (uveden rok studia). Barevná výplň: černá two records of such birds at the same site – železnice; nachová – průmyslové oblasti; červená – hustě zastavěné oblasti (centrum (within ca. 1 km for larger and 0.5 km města); oranžová – řídce zastavěné oblasti; for smaller species) during two different tmavě zelená – lesy; světle zelená – parky; surveys, and all found nesting sites were modrozelená – trávníky; žlutá – orná půda. assumed as representing an occupied

44 SYLVIA 53 / 2017 territory. For a territory exceeding the city (i.e., study area) boundaries, there boundary of the study area, only ½ of it were no such cases in this study. should be taken into account while cal- To compare differences in the popula- culating population density (Bibby et al. tion density of woodpeckers in the out- 2012). However, due to the large size of er and inner zones, ecological density the study area, and a clear confinement (pairs per 1,000 ha of wooded areas) of of most woodpecker species to wooded each woodpecker species was calculated areas, which were not dissected by the for all wooded areas (forests, parks and

Fig. 2. Distribution of Black Woodpecker Fig. 4. Distribution of Green Woodpecker (Dryocopus martius ) territories in the city (Picus viridis ) territories in the city of of Wrocław during the years 2003–2010. For Wrocław during the years 2003–2010. For map explanations see Fig. 1. map explanations see Fig. 1. Obr. 2. Rozmístění teritorií datla černého Obr. 4. Rozmístění teritorií žluny zelené (Dryocopus martius ) ve Vratislavi v období (Picus viridis) ve Vratislavi v období 2003– 2003–2010. Vysvětlivky k mapě viz obr. 1. 2010. Vysvětlivky k mapě viz obr. 1.

Fig. 3. Distribution of Grey-headed Wood- Fig. 5. Distribution of Syrian Woodpecker pecker (Picus canus) territories in the city (Dendrocopos syriacus) territories in the city of Wrocław during the years 2003–2010. For of Wrocław during the years 2003–2010. For map explanations see Fig. 1. map explanations see Fig. 1. Obr. 3. Rozmístění teritorií žluny šedé ( Picus Obr. 5. Rozmístění teritorií strakapouda jižní- canus) ve Vratislavi v období 2003–2010. ho ( Dendrocopos syriacus ) ve Vratislavi v ob- Vysvětlivky k mapě viz obr. 1. dobí 2003–2010. Vysvětlivky k mapě viz obr. 1.

45 Kopij G. / Woodpeckers in the inner and outer zones of a city

all other wooded areas). For each woodpecker species, the crude density was also calculated (pairs per 1,000 ha of the whole study area). Maps were generated to show the distribution of breeding pairs of all woodpecker species (Fig. 2–8). The distribution is shown on the background of habitats in the city of Wrocław.

Fig. 8. Distribution of Lesser Spotted Woodpecker ( Dryobates minor ) territories in the city of Wrocław during the years 2003– 2010. For map explanations see Fig. 1. Obr. 8. Rozmístění teritorií strakapouda ma- lého (Dryobates minor ) ve Vratislavi v období 2003–2010. Vysvětlivky k mapě viz obr. 1.

RESULTS Fig. 6. Distribution of Great Spotted In total, seven woodpecker species Woodpecker ( Dendrocopos major ) territo- were recorded as breeding in the city ries in the city of Wrocław during the years of Wrocław during the years 2003–2010 2003–2010. For map explanations see Fig. 1. (Table 1). Most Black Woodpecker terri- Obr. 6. Rozmístění teritorií strakapouda velké- tories were located in the north-western ho ( Dendrocopos major ) ve Vratislavi v obdo- part of the city, where there are the bí 2003–2010. Vysvětlivky k mapě viz obr. 1. largest forests (Fig. 2). The Grey-headed Woodpecker occurred along rivers (Fig. 3), while the Green Woodpecker was quite evenly distributed all over the city (Fig. 4). The Syrian Woodpecker was rare as only two probably breeding pairs were recorded (Fig. 5). Most breeding territories of the Great and Middle Spotted Woodpeckers occurred in the north-western part of the city, where there are the largest forests (Fig. 6 and 7), while the Lesser Spotted Woodpecker was equally common in the north-west- Fig. 7. Distribution of Middle Spotted ern and eastern parts of the city (Fig. 8), Woodpecker ( Dendrocoptes medius ) territo- where larger wetland areas occur. ries in the city of Wrocław during the years The Great Spotted Woodpecker was 2003–2010. For map explanations see Fig. 1. Obr. 7. Rozmístění teritorií strakapouda by far the most abundant species, mak- prostředního ( Dendrocoptes medius ) ve ing up more than a half of all woodpeck- Vratislavi v období 2003–2010. Vysvětlivky er breeding pairs. The Middle Spotted k mapě viz obr. 1. and Lesser Spotted Woodpeckers were

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Table 1. Population densities of woodpecker species in the outer and inner zones of the city of Wrocław in 2003–2010. N – number of breeding pairs, D c – crude density (pairs per 1,000 ha of the whole area), D e – ecological density (pairs per 1,000 ha of wooded areas). Tab. 1. Populační hustota „datlů“ ve vnější a vnitřní zóně města Vratislavi. N – počet hnízdících párů, Dc – hrubá populační hustota (páry na 1 000 ha celkové rozlohy), D e – ekologická popu- lační hustota (páry na 1 000 ha porostů dřevin).

outer zone / vnější inner zone / vnitřní total / celkem zóna (19,300 ha, zóna (10,000 ha, (29,300 ha, 3,200 ha species / druh 2,380 ha of woods / 820 ha of woods / of woods / porostů dřevin ) porostů dřevin ) porostů dřevin )

NDc De NDc De NDc De Black Woodpecker 17 0.9 7.1 4 0.4 4.9 21 0.7 6.6 Dryocopus martius Grey-headed Woodpecker 8 0.4 3.4 6 0.6 7.3 14 0.5 4.4 Picus canus Green Woodpecker 25 1.3 10.5 19 1.9 23.2 44 1.5 13.8 Picus viridis Syrian Woodpecker 0 0 0 2 0.2 2.4 2 0.1 0.6 Dendrocopos syriacus Great Spotted Woodpecker 158 8.2 66.4 42 4.2 51.2 200 6.8 62.5 Dendrocopos major Middle Spotted Woodpecker 34 1.8 14.3 6 0.6 7.3 40 1.4 12.5 Dendrocoptes medius Lesser Spotted Woodpecker 31 1.6 13.0 6 0.6 7.3 37 1.3 11.6 Dryobates minor total / celkem 273 14.2 114.7 85 8.5 103.6 358 12.2 111.9 also relatively numerous. Both nested 114.7 versus 103.6 pairs per 1,000 ha of in a similar density of 11–12 pairs per wooded areas. In the typical forest spe- 1,000 ha of wooded areas. The propor- cies such as the Black, Great, and Middle tion of abundance among these three Spotted Woodpecker, the ecological den- woodpecker species was: Great Spotted sities in the inner zone reached 51– 77% Woodpecker 0.72 : Middle Spotted of densities in the outer zone, while in Woodpecker 0.14 : Lesser Spotted the species associated with semi-open Woodpecker 0.14 (N = 277 pairs of all woodlands (Grey-headed and Green three species). Both the Grey-headed Woodpecker), the ecological densities Woodpecker and the Green Woodpecker in the inner zone reached 215–221% of were relatively common in Wrocław. The the densities in the outer zone. former was, however, three times less In the forest-steppe woodpecker spe- numerous than the later one. Also, the cies, i.e. the Grey-headed and Green Black Woodpecker was found to be rela- Woodpecker, the ecological density tively numerous (Table 1). could not be precisely calculated, as The overall population densities of it was difficult to estimate the size of all woodpecker species were consider- the available potential habitat of these ably higher in wooded areas in the outer species (a mosaic of small wooded ar- than in the inner zone of the city, namely eas and wood edges together with riv-

47 Kopij G. / Woodpeckers in the inner and outer zones of a city

35 forests / lesy 30 parks / parky 25 20 15 populační hustota 10 5 density / 0 0 100 200 300 400 500 600 700 wood patch size / plocha porostu (ha)

Fig. 9. Relationship between the overall woodpecker population density (pairs per 100 ha of wooded habitats) and the wood patch size in the city of Wrocław. Data for 10 forests and 10 parks listed in Appendix 1. Obr. 9. Vztah mezi celkovou populační hustotou „datlů“ (páry na 100 ha porostů dřevin) a rozlohou studijní plochy ve Vratislavi. Data pro 10 lesů a 10 parků uvedených v příloze 1.

8 forests / lesy parks / parky 6 počet druhů 4

no. of species / 0 0 100 200 300 400 500 600 700 wood patch size / plocha porostu (ha)

Fig. 10. Relationship between the number of woodpecker species and the wood patch size in the city of Wrocław. Data for 10 forests and 10 parks listed in Appendix 1. Obr. 10 . Vztah mezi počtem druhů „datlů“ a rozlohou studijní plochy ve Vratislavi. Data pro 10 lesů a 10 parků uvedených v příloze 1. ers, meadows, fields and other open 1,000 ha; Table 1). However, for all forest habitats). If the crude density is taken woodpecker species pooled, the crude into account, the population density of density in the outer zone more than the Grey-headed Woodpecker was only doubled that in the inner zone (Table 1). slightly higher in the inner than in the The density of woodpeckers declined outer zone (0.6 vs. 0.4 pairs per 1,000 ha). with the increase in the size of the study This difference in the crude density was, plot (Fig. 9), while the number of wood- however, quite high in the case of the pecker species increased with wood Green Woodpecker (1.9 vs. 1.3 pairs per patch size (Fig. 10).

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DISCUSSION species may extend their breeding season (usually breeding earlier than in the Population density and species non-urban habitats), reduce migratory diversity ability and increase breeding success Noticeable differences were recorded (Chamberlain et al. 2009). in population densities of woodpeckers The data on woodpecker abundance breeding in the outer and inner zones collected in Wrocław suggest that at of the city of Wrocław. Typical forest least three woodpecker species, name- species (Black, Great Spotted, Middle ly the Black, Grey-headed and Green Spotted Woodpecker) nested in higher Woodpecker, have increased in numbers densities in the outer than in the inner in the last few decades (cf. Szarski 1955, zone. It should be pointed out, how- Lontkowski et al. 1988, Dyrcz et al. 1991). ever, that woods are less fragmented in However, due to a lack of comparative the outer than in the inner zone, and quantitative studies from the past, it is fragmentation is known to negatively impossible to determine any trends in affect woodpecker densities (Kosiński population densities of any of the wood- & Kempa 2007, Myczko et al. 2014). In pecker species separately for the inner the case of forest-steppe woodpecker and outer zone of the city. Myczko et species, population density of both the al. (2014) have shown a decrease in the Grey-headed and Green Woodpecker woodpecker species richness and their was higher in the inner than in the outer abundance with the decrease of the zone, which may suggest an increase distance from the Poznań city centre. along the urbanization gradient. They pointed out that larger wood patch It has been documented that most size may mitigate this negative effect, woodpeckers respond negatively to in- especially in the case when woods are creasing urbanization (Chace & Walsh multi-layered and comprise a larger pro- 2006). The following factors may play portion of deciduous trees. a role: the size of wooded areas, tree Seven woodpecker species recorded species composition, structure and age in the city of Wrocław is a similar num- of tree stands, presence of dead trees, ber to that recorded in other big cities competition with other species, and in Poland, such as Warsaw (Luniak et presence of predators. In urban environ- al. 2001), Łódź (Janiszewski et al. 2009) ments, especially in the inner zone, the and Poznań (Myczko et al. 2014), and in wooded areas are usually of a relatively other cities in Central European coun- small size, and this may be the main fac- tries (Mitschke & Baumung 2001, Otto tor selecting against most woodpecker & Witt 2002, Wichmann & Frank 2005). species. However, the species of the However, either the Green Woodpecker genus Picus are less dependent on forest or Grey-headed Woodpecker was re- size. They are typically inhabitants of the corded in all these cities, while both forest-steppe zone and may benefit from species occur and are relatively common urbanization, as it fragments continuous breeding residents only in Wrocław. The forests, resulting in greater heterogene- Grey-headed Woodpecker occurs in cit- ity of the land cover (Chamberlain et al. ies situated only in southern Poland 2009). Species is considered urbanized (Tomiałojć & Stawarczyk 2003). The when it increases its abundance along Syrian Woodpecker is a newcomer to the urban gradient (from rural areas to the Polish avifauna. It started to breed in the city centre). In addition, urbanizing the country in the late 1970s (Michalczuk

49 Kopij G. / Woodpeckers in the inner and outer zones of a city

2014). In Silesia (SW Poland) it is known the mapping method are not accurate to breed only in a few isolated sites. Its enough to make a proper comparison breeding in Wrocław had not been docu- (see the separate chapter below). They mented before. However, in some cities may, however, indicate general tenden- situated in the Vistula valley (Kraków cies. The differences in population densi- and Warsaw) and eastwards from this ties of woodpeckers in the selected big- river (Lublin, Zamość, Przemyśl), it is gest Polish cities cannot be linked to dif- a well-established breeding resident, ferent geographical locations, as Warsaw with 20–40 pairs recorded in each of and Łódź are situated much closer to each these cities (Luniak et al. 2001, Biaduń other than to Wrocław. Also, the structure 2001, Tomiałojć & Stawarczyk 2003, and age of woods is similar in Łódź and Fröhlich & Ciach 2013, Michalczuk 2014). Warsaw. However, quantitative studies on Other investigations conducted using woodpeckers were conducted in Warsaw the simplified territory mapping method during the years 1986–1990, therefore in all wooded areas in Warsaw (Luniak about 15–20 years earlier than in Łódź et al. 2001) and Łódź (Janiszewski 2009) and Wrocław. It may be concluded that have shown that the Black, Green and the differences were due to a real in- Middle Spotted Woodpeckers nested crease in numbers of the Black, Green in the same densities in Wrocław and and Middle Spotted Woodpeckers over Łódź, but in much lower densities in the last 15–20 years in Poland (Tomiałojć Warsaw (Table 2; no distinction was made & Stawarczyk 2003). Such increase over by the authors between the inner and the last few decades has been evidenced outer zones in these cities). It should in Wrocław in all these three species and be stressed, however, that the results also in the Grey-headed Woodpecker (cf. obtained by the simplified version of Szarski 1955, Dyrcz et al. 1991, Kopij 2010,

Table 2. Population densities of woodpeckers (breeding pairs per 1,000 ha of wooded areas) in selected Polish cities. Tab. 2. Populační hustoty „datlů“ (hnízdící páry na 1 000 ha porostů dřevin) ve vybraných městech v Polsku. city / město Warsaw Łódź Wrocław whole area / celková rozloha 494 km 2 293 km 2 293 km 2 wooded areas / plocha porostů dřevin 143.3 km 2 28.4 km 2 32 km 2 study period / období 1986–1990 2001–2008 2002–2010 Black Woodpecker / datel černý 1.0 5.3 5.9 Grey-headed Woodpecker / žluna šedá 0.0 0.0 3.9 Green Woodpecker / žluna zelená 2.8–4.2 15.1–15.8 12.3 Syrian Woodpecker / strakapoud jižní 1.4–2.8 0.4 0.6 Great Spotted Woodpecker / strakapoud 20.9–34.9 105.6–140.8* 55.9 velký Middle Spotted Woodpecker / strakapoud 2.1–3.5 12.0–14.1 11.2 prostřední Lesser Spotted Woodpecker / strakapoud 5.6–10.5 39.8–45.8* 10.3 malý source / zdroj Luniak et al. Janiszewski et al. this study / (2001) (2009) tato práce * values most probably overestimated / hodnoty nejspíše nadhodnocené

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2014a,b,c, 2016a). It does not mean that densities of woodpeckers in the inner this increase in population density oc- and outer zones in those cities. It is, there- curred also in the wooded areas in the fore, difficult to determine whether the inner zone. Nevertheless, it may indi- woodpeckers really infiltrate into the cit- cate an urbanization process in some ies and whether they undergo the urbani- woodpecker species taking place in zation process. Poland in the few recent decades. This It has been shown convincingly urbanization process is especially perti- that the ecological population density nent to the Green Woodpecker, which of woodpeckers (per wooded area) in was recorded as nesting even in the city large woodlands and in farmlands with centres in Warsaw (Luniak et al. 2001), highly fragmented forests is the same Łódź (Janiszewski et al. 2009), Wrocław (Tjernberg et al. 1993), although this (this study), and also in Berlin (Otto & could be species-specific. In most cases, Witt 2002) and Hamburg (Mitschke & the ecological population densities of Baumung 2001). However, there is a lack woodpeckers recorded in Wrocław are of comparative analyses of population higher than those recorded in forest

Table 3. Ecological population densities of woodpeckers (breeding pairs per 1,000 ha of wooded areas) in the Wrocław city and outside the cities in selected regions in SW Poland during the years 2001–2010. Explanations: DM – Black Woodpecker, PC – Grey-headed Woodpecker, PV – Green Woodpecker, DE – Middle Spotted Woodpecker, DI – Lesser Spotted Woodpecker. The Great Spotted Woodpecker was excluded in the studies outside the city of Wrocław . Tab. 3. Ekologické populační hustoty „datlů“ (hnízdící páry na 1 000 ha porostů dřevin) ve Vratislavi a mimo města v různých regionech jz. Polska v letech 2001–2010. Vysvětlivky: DM – datel černý, PC – žluna šedá, PV – žluna zelená, DE – strakapoud prostřední, DI – strakapoud malý. Strakapoud velký nebyl ve studiích mimo Vratislav zahrnut.

whole forests / area / region / porosty forest type / source / celková DM PC PV DE DI oblast dřevin typ porostu zdroj rozloha (km2) (km2) Wrocław, 200 23.8 oak, pine / dub, 7.1 3.4 10.5 14.3 13.0 this study / outer zone borovice tato práce / vnější zóna Wroclaw, 93 8.2 oak / dub 4.9 7.3 23.2 7.3 7.3 this study / inner zone tato práce / vnitřní zóna Grądy 35 15 oak, mixed / 2.7 6.0 6.0 3.3 10.0 Kopij 2015 Odrzańskie dub, smíšený Niemodlin 300 120 pine, spruce / 2.8 0.4 0.1 0.7 0.4 Kopij 2016b Land borovice, smrk Niemodlin 200 195 pine / borovice 2.6 0.2 0.0 0.1 0.1 Kopij 2016c Forest Nysa Land 720 15 mixed / smíšený 8.7 3.3 6.0 8.7 8.7 Kopij 2012 Grodków 584 70 oak, mixed / 1.7 1.0 0.6 – 0.7 Kopij 2006 Land dub, smíšený

51 Kopij G. / Woodpeckers in the inner and outer zones of a city fragments in farmland, as well as in There is a possibility that densities less fragmented forests (Table 3). The of woodpecker species with large ter- reason for this could be that there are ritories (e.g., Black Woodpecker) have probably larger proportions of old oaks been overestimated in this study. In in most wooded areas in Wrocław than some neighbouring wood patches, the in the neighbouring areas. Milder win- same pair could have been counted ter weather conditions in Wrocław than twice. It is well known that drumming outside the city (Smolnicki & Szykasiuk in some woodpecker species and ter- 2002) may also play a role in that regard. ritorial calls in others are performed by both male and female. Considering this, Methodical considerations special attention was paid to avoid dou- There are many sources of bias and lack ble counts in this study, especially in of precision regarding the population the Black Woodpeckers, Grey-headed estimation of woodpeckers, such as the Woodpeckers and Green Woodpeckers. selection of the counting method or In the cases when calling birds were re- size of the study area. The simplified corded close to each other (closer than version of the mapping method could 1 km apart), or called simultaneously provide a source of bias as clusters (two birds heard at the same time), an of records are important while inter- attempt was made to determine whether preting the data. In the present study, these were calls uttered by a male and fe- four repeated counts could not produce male of the same pair or by two separate enough records for an accurate inter- males. Nevertheless, the birds may some- pretation of the clusters. times fly over a distance longer than 1 km There is a certain misconception re- and could be counted as separate pairs. garding the counting method in wood- In the present study, the densities of peckers. Nest finding combined with terri- woodpeckers declined with the increase tory mapping (Tomiałojć 1980) is certainly in the size of the study area, whilst a pos- the most accurate method. However, it is itive relationship was found between too time-consuming and, therefore, practi - the number of woodpecker species and cally not applicable in large study plots. wood patch size. These correlations were The playback technique may be more only slightly different in the inner (parks) appropriate in such situation. Using this and outer zone (forests). The correlation method, one survey conducted in March/ between woodpecker population density April may be often sufficient to estimate and wood patch size has been also evi- population densities of most woodpeck - denced by Gaston et al. (1999), Kosiński er species (Kosiński & Winiecki 2005, & Winiecki (2005) and Kosiński & Kempa Kosiński & Kempa 2007). Most of them (2007). The reason for such correlation are highly territorial and as such very vo - is probably a strong tendency among cal in the pre-laying period during the researchers to choose plots of the most phase of territory establishment in early optimal habitats for population estimates spring (March/April in Central Europe). of the selected species, while suboptimal However, under sunny and windless con - and marginal habitats are neglected by ditions, it is easy to detect woodpeck- those researchers. In large study plots, ers and estimate their population density both optimal and suboptimal habitats in that peak period of their vocal activ - are more likely to be represented, and ity, even without playback (e.g., Kopij & the results obtained from such areas are Hołga 2008, Walankiewicz et al. 2011). therefore more reliable, even if less ac-

52 SYLVIA 53 / 2017 curate. To overcome this notorious bias redukovaný keřový podrost a zahrnují of selecting attractive plots for population i exotické druhy dřevin. Zastoupení více studies, it is recommended that, at least než stoletých stromů zde přesahuje 50 %. for species with large territories and with Rozloha parků se pohybuje od 2 do 120 low population densities, only large study ha (medián = 17,8 ha) a jejich celková plots should be designed for population plocha je 781 ha. Ostatní porosty dřevin, density estimations. On the other hand, jako skupiny stromů, aleje, živé ploty atp., it is more difficult to precisely estimate jsou rozptýleny po celém území, ale nej - population densities of selected species častější jsou v jihovýchodní části města. on larger areas and the probability of Jejich celková plocha je 133 ha. underestimation is higher in larger than Studijní plocha města byla rozděle - in smaller plots. na na vnitřní (cca 1/3 celkové rozlohy; Finally, there are marked year-to- více než 50 % zastavěné plochy; porosty year fluctuations in the population dřevin 820 ha) a vnější zónu města densities of some woodpecker species, (méně než 50 % zastavěné plochy, po- caused mainly by winter weather con- rosty dřevin 2 380 ha; obr. 1). Většina ditions (snowfall and snow cover; e.g. parků se nachází ve vnitřní zóně města, Wesołowski & Tomiałojć 1986, Christen zatímco většina lesů ve vnější zóně. Byla 1994). Given that the present study was použita zjednodušená metoda mapová- conducted over the period 2003–2010, ní hnízdních okrsků. Všechny porosty the distribution of territories may be dřevin v katastru města byly navštíveny heterogeneous among years/plots. čtyřikrát v hnízdní sezóně. Po jednom However, the mild climate in the study snímku bylo provedeno v dubnu, květnu, area is not expected to cause substantial červnu a červenci. Různé části města fluctuations in woodpecker densities. byly zkoumány v různých letech (každá plocha vždy jen v jednom roce; obr. 1). Bylo zaznamenáno sedm druhů „dat- SOUHRN lů“ (tab. 1, obr. 2–8) s následujícími eko- V období 2003–2010 jsem mapoval te- logickými populačními hustotami (páry ritoria „datlů“ na 293 km 2 území města na 1 000 ha porostů dřevin): strakapoud Vratislavi (jz. Polsko). Území zahrnovalo velký ( Dendrocopos major ) – 62,5, žlu- 32 km 2 ploch s porosty dřevin: 13 příměst - na zelená ( Picus viridis ) – 13,8, straka- ských lesů, 44 parků a řadu menších ploch poud prostřední ( Dendrocoptes medi- s rozptýlenou zelení. Příměstské lesy jsou us ) – 12,5, strakapoud malý ( Dryobates využívány k produkci dřeva a tvoří je minor ) – 11,6, datel černý ( Dryocopus zapojené porosty původních dřevin s vy - martius ) – 6,6, žluna šedá ( Picus canus ) vinutým keřovým patrem (většinou spole - – 4,4 a strakapoud jižní ( Dendrocopos čenstvo Tilio-Carpinetum ). Stáří porostů syriacus ) – 0,6. Souhrnná ekologická se většinou pohybuje mezi 50 a 100 lety. populační hustota všech druhů „datlů“ Rozloha lesů se pohybuje od 10 do 680 byla vyšší ve vnější oproti vnitřní zóně ha (medián = 175,8 ha) a jejich celková města – 114,7 oproti 103,6 párům na plocha je 2 286 ha. Parky jsou částečně 1 000 ha porostů dřevin. Ekologické po- otevřené plochy s porosty dřevin, seče - pulační hustoty typických lesních druhů nými trávníky, hřišti, řídce rozptýlenými „datlů“ (datel černý, strakapoud velký, budovami atp. Podobně jako lesy, větši - strakapoud prostřední) ve vnitřní zóně na parků náleží ke společenstvu Tilio- města dosahovaly 51–77 % hustot za- Carpinetum . Oproti lesům mají výrazně znamenaných ve vnější zóně, zatímco

53 Kopij G. / Woodpeckers in the inner and outer zones of a city hustoty lesostepních druhů (žluna zelená jsou zahrnuty všechny přítomné biotopy a šedá) ve vnitřní zóně města dosahovaly a výsledky jsou tedy reprezentativnější. 215–221 % hustot zaznamenaných ve Na druhou stranu zde hrozí podhodnoce- vnější zóně. V případě lesostepních dru- ní velikosti populace, protože velké plochy hů, jako je žluna šedá a zelená, nemohla je obtížné pečlivě prozkoumat. být ekologická hustota přesně odhadnuta, protože u rozptýlené zeleně je obtížné sta- novit plochu obývaného biotopu. Proto LITERATURE byla spočítána i hrubá populační hustota Bauer H.-G. & Berthold P. 1997: Die Brutvögel (páry na 1 000 ha celkové rozlohy studo- Mitteleuropas: Bestand und Gefährdung . vané oblasti). Hrubé populační hustoty AULA-Verlag, Wiesbaden. žluny šedé ve vnitřní zóně města byly Biaduń W. 2001: Ekspansja dziecioła białoszy- mírně vyšší než ve vnější zóně (0,6 vs. 0,4 jego Dendrocopos syriacus w Lublinie. In: Indykiewicz P., Barczak T. & Kaczorowski párů na 1 000 ha). V případě žluny zele- G. (eds): Bioróżnorodność i ekologia né byly hrubé populační hustoty výrazně- populacji zwierzęcych w środowiskach ji vyšší ve vnitřní zóně města (1,9 vs. 1,3 zurbanizowanych . Wydawnictwo NICE, párů na 1 000 ha). U všech lesních druhů Bydgoszcz: 232–235. „datlů“ byly hrubé populační hustoty ve Bibby C. J., Burgess N. D. & Hill D. A. 2012: vnější zóně přibližně dvojnásobné oproti Bird Census Techniques . Academic Press, hustotám ve vnitřní zóně (tab. 1). London. Populační hustoty zaznamenané ve Bryś K. & Bryś T. 2010: Reconstruction of the Vratislavi byly podobné jako v dalších 217-year (1791–2007) Wrocław air tempe- větších městech v Polsku (vnější a vnitřní rature and precipitation series. Bulletin of Geography 3: 121–171. zóna města nebyla v těchto studiích roz- Chace J. F. & Walsh J. J. 2006: Urban effects lišována; tab. 2), ovšem ve většině pří- on native avifauna: a review. Landscape & padů byly ekologické populační hustoty Urban Planning 74: 46–69. vyšší ve Vratislavi než v krajině mimo Chamberlain D. E., Cannon A. R., Toms M. P., město či méně fragmentovaných lesích Leech D. I., Hatchwell B. J. & Gaston K. J. (tab. 3). Vysvětlením může být vyšší za- 2009: Avian productivity in urban landsca- stoupení starých dubů ve velké části po- pes: a review and metaanalysis. Ibis 151: rostů dřevin ve Vratislavi. Mírnější zimy 1–18. ve Vratislavi oproti krajině mimo město Christen W. 1994: Bestandsentwicklung von Grünspecht Picus viridis und Grauspecht (Smolnicki & Szykasiuk 2002) mohly Picus canus nordlich von Solothurn také sehrát svou roli. 1980–1993. Ornithologische Beobachter Populační hustoty „datlů“ klesaly se 91: 49–58. vzrůstající rozlohou studijní plochy (obr. Czyż S. 2008: Atlas ptaków lęgowych 9), zatímco počet druhů „datlů“ s plo- Częstochowy 2003–2007. Wydawnictwo S. chou rostl (obr. 10, viz také příloha 1). Czyż, Częstochowa. Negativní korelace mezi populační husto- Del Hoyo J., Collar N. J., Christie D. A., Elliott tou „datlů“ a velikostí vzorkované plochy A. & Fishpool L. D. C. 2014: HBW and je obecně známým faktem (Gaston et al. BirdLife International Illustrated Checklist of the Birds of the World. Volume 1: Non- 1999, Kosiński & Winiecki 2005, Kosiński passerines . Lynx Edicions, Barcelona, & Kempa 2007). Důvodem je zřejmě ten- BirdLife International, Cambridge. dence výzkumníků upřednostňovat při Dunn A. M. & Weston M. A. 2008: A review studiu malých území plochy s optimálním of terrestrial bird atlases of the world and biotopem, zatímco méně kvalitní biotopy their applica tion. Emu 108: 42–67. jsou opomíjeny. Při studiu velkých území Dyrcz A., Grabiński W., Stawarczyk T.

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Appendix 1. Numbers of breeding pairs of woodpeckers in larger forests and parks in the city of Wrocław. Explanations: DM – Black Woodpecker, PC – Grey-headed Woodpecker, PV – Green Woodpecker, DA – Great Spotted Woodpecker, DE – Middle Spotted Woodpecker, DI – Lesser Spotted Woodpecker. Syrian Woodpecker: single probably breeding pairs recorded in the Szczytnicki and Skowroni/Andersa parks. Příloha 1. Počet hnízdících párů „datlů“ ve větších lesích a parcích ve městě Vratislavi. Vysvětlivky: DM – datel černý, PC – žluna šedá, PV – žluna zelená, DA – strakapoud velký, DE – strakapoud prostřední, DI – strakapoud malý. Strakapoud jižní: po jednom pravděpodobně hnízdícím páru zaznamenáno v parcích Szczytnicki a Skowroni/Andersa.

area forest type (ha) total / locality / lokalita DM PC PV DA DE DI / typ porostu / roz- celkem loha forests / lesy (outer zone / vnější zóna*) Mokrzański conifers / 680 3 21 3 27 jehličnany Ratyński conifers / 295 1 1 1 13 1 2 19 jehličnany Rędziński oak / dub 218 2 1 12 6 4 25 Lesnicki oak / dub 190 3 1 1 23 8 4 40 Strachociński oak / dub 139 1 13 6 1 21 Osobowicki oak / dub 138 1 2 10 4 3 20 Kosmonautów mixed / smíšený 138 1 1 1 1 4 Pilczycki oak / dub 88 1 1 2 14 2 20 Lesicki pine / borovice 38 1 3 1 5 Bystrzycki oak / dub 35 1 1 6 1 9 total / celkem 1,959 13 5 10 115 32 15 190 parks / parky (inner zone / vnitřní zóna*) Szczytnicki oak / dub 100 2 4 7 3 2 18 Tysiąclecia mixed / smíšený 90 1 2 3 Zachodni oak / dub 75 1 1 7 9 Grabinszyńki mixed / smíšený 48 1 1 1 5 8 Wschodni oak / dub 411 1 1 5 1 2 11 Sołtysowicki oak / dub 32 1 2 1 5 1 10 Skowroni/ mixed / smíšený 31 1 2 1 4 Andersa Poludniowy oak / dub 25 1 2 3 Pilczycki oak / dub 21 1 1 4 6 Popowicki oak / dub 17 1 1 3 5 total / celkem 480 8 5 14 41 5 4 77 *Only two smaller forests (Kuźnicki – 9.4 ha, and Rakowiecki – 22.4 ha) were situated in the inner zone, and four small parks (>10 ha) and two (c. 20 ha) were in the outer zone (not included in this table).