Status of the globally threatened Aquatic Warbler (Acrocephalus paludicola) in the Czech Republic

Sylvia 49 / 2013

Status of the globally threatened Aquatic Warbler (Acrocephalus paludicola) in the Czech Republic Celosvětově ohrožený druh rákosník ostřicový (Acrocephalus paludicola) v České republice Jiří Flousek1, Jaroslav Cepák2 rkonoše National Park Administration, Dobrovského 3, CZ-543 01 Vrchlabí; K e‑mail: [email protected] 2 Bird Ringing Centre, National Museum, Hornoměcholupská 34, CZ-102 00 Praha 10-Hostivař; e‑mail: [email protected] 1

Flousek J. & Cepák J. 2013: Status of the globally threatened Aquatic Warbler (Acrocephalus paludicola) in the Czech Republic. Sylvia 49: 1–20. The paper summarises data on occurrence of the Aquatic Warbler (Acrocephalus paludicola) in the territory of the present Czech Republic in 1946–2011. Altogether 129 individuals were ringed, 85 visual observations of 108 birds were made and 3 dead specimens were recorded during the study period. In both ringed and observed individuals, records from the period of spring migration prevail. Based on ringing data, the spring passage peaked in the 3rd ten-day period of April. Concerning the records of observed birds, the passage did not show any distinct peak (most observations come from the 1st–3rd ten-day period of May). In the breeding season (1 June – 19 July), no birds were captured but 22 observations of 25 individuals, including singing males, were made. However, breeding of the species has not been documented in the country so far. The autumn migration occurred from the 3rd ten-day period of July with a peak in the 1st or 2nd ten-day period of September (ringing data and visual observations pooled). Almost 80% of the records come from central and southern Bohemia, from the Bohemian‑Moravian Highlands and northern Moravia. Most of the ringed birds were captured in lowlands (mean altitude 258 m a.s.l., median 210 m, n = 129), while in the observed birds the mean altitude was 334 m (median 240 m, n = 85). Altogether 71% of the captured birds were recorded in a specific habitat type – on the margin of reed beds continuing to low sedges, or in wet meadows. Most (63%) of the observed and captured birds were recorded at sites with no protection status, 37% in protected areas. Long-term trend in the number of captured Aquatic Warblers, in relation to ringing effort, suggests that the number of birds passing through the country has declined since 1960. Despite that, the obtained data confirm that there still are important stopover sites of the Aquatic Warbler in the country and the Czech Republic thus ranks among range states of this globally threatened species. Studie hodnotí celkem 240 nálezů rákosníka ostřicového (Acrocephalus paludicola) v České republice z období 1946–2011. Jarní tah dle kroužkovacích dat vrcholil ve 3. dekádě dubna, nejvíce pozorovaných ptáků bylo zastiženo až v průběhu celého května. V hnízdním období bylo zaznamenáno 25 jedinců, včetně zpívajících samců, hnízdění však nebylo doloženo. Podzimní tah probíhal od 3. dekády července s vrcholem výskytu v 1. (kroužkovací data), resp. ve 2. zářijové dekádě (pozorovaní ptáci). Téměř 80 % nálezů pocházelo ze středních a jižních Čech, z Českomoravské vrchoviny a severní Moravy. Průměrná nadmořská výška výskytu dosahovala 258 m u kroužkovaných a 334 m u pozorovaných ptáků. Většina (71 %) jedinců byla zjištěna na okrajích rákosin a nízkých ostřic, nebo na vlhkých loukách; asi třetina nálezů (37 %) pocházela z chráněných území. Dlouhodobý trend naznačuje, že zhruba od roku 1960

1

Flousek J. & Cepák J. / Aquatic Warbler in the Czech Republic

dochází ke snižování počtu rákosníků ostřicových protahujících přes naše území. Přesto se u nás stále nacházejí důležité migrační zastávky a Česká republika tak patří mezi areálové státy tohoto celosvětově ohroženého druhu. Keywords: Aquatic Warbler, Acrocephalus paludicola, Czech Republic, status, migration, occurrence

INTRODUCTION The Aquatic Warbler (Acrocephalus paludicola) is currently classified as the rarest and most threatened passerine species in continental Europe. Due to that, it has been included in the IUCN Red List of Threatened Species in the category “vulnerable” (BirdLife International 2012), as well as in Appendices I and II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS, Bonn Convention). Appendix I of the CMS includes species which are critically endangered throughout all or a significant proportion of their range and which require strict and direct protection. Appendix II of the CMS lists endangered animal species which would benefit from specially focused international agreements (memoranda), concluded by countries with occurrence of a certain species or a group of systematically related or ecologically similar species. Such agreements should ensure or restore favourable conditions for long-term survival of the particular migratory species based on cooperation of signatory countries. One of the existing agreements is the Memorandum on Understanding Concerning Con servation Measures for the Aquatic Warbler, which became effective on 30 April 2003 and has been signed by 16 out of 22 range states so far. In the past, breeding range of the Aquatic Warbler was more or less continuous, forming a wide belt from western through central and eastern Europe 2

to western Siberia, i. e. including the currently unoccupied countries of western and southern Europe, such as France, Belgium, the Netherlands, Italy or Romania. Since the end of the 19th century, extensive fragmentation of the breeding range has occurred as a result of rapid destruction of breeding habitats. At present, the species has been surviving at a few isolated sites only (Schulze-Hagen 1991, Dyrcz & SchulzeHagen 1997, Dyrcz 2006). Current size of the global population of the Aquatic Warbler is estimated at 11,000–16,000 singing males. Almost 95% of them breed in three range states only – Belarus, Poland and Ukraine. Population decline is dramatic – on average by 40% in ten years (AWCT 2012, BirdLife International 2012). Distribution range of the Aquatic Warbler is highly fragmented. The species has been recorded at less than 50 breeding sites with an estimated area of only 375 km2 (Zadrąg et al. 2011) in 6 countries; however, three quarters of the population are restricted to two river systems – Pripyat/Yaselda in Belarus and Biebrza/Narew in Poland. The main threat affecting the Aquatic Warbler is the loss of suitable habitats at breeding sites, stopover sites and wintering grounds, caused mostly by changes in water regime at the particular sites (soil improvement, peat mining, canalization of watercourses, construction of dams etc.) or by abandonment of traditional farming practices (grazing, regular mowing). The most important breeding

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habitats of the species are wet shortgrass (especially sedge) meadows with water level not exceeding 10–15 cm; at wintering grounds the species inhabits wetlands with a similar vegetation structure; during migration it is usually recorded on margins of sedge or reed beds adjacent to open water surface (e.g. Kozulin & Flade 1999, Provost et al. 2010, Tannenberger et al. 2010, Arbeiter & Tegetmeyer 2011, Flade et al. 2011). Key Central-European populations in Belarus (3,940–6,300 singing males), in northeastern Poland (2,670–3,850) and in Ukraine (2,000–4,600) seem to be stable, mainly thanks to significant conservation measures (see e.g. Dézécot et al. 2008, Zadrąg et al. 2011). On the other hand, the number of Aquatic Warblers in marginal breeding populations has been declining dramatically – in GermanPolish Pomerania less than 60 males breed at present, in Hungary the population has dropped from 700 to 3–5 pairs during less than ten years, in Lithuania it is estimated at 110–309 males (AWCT 2012, BirdLife International 2012). In the West-Siberian part of the range, the species has most probably become extinct already. The situation at African wintering grounds in the Sahel region is also critical. These areas are threatened by rapid and extensive development of agriculture (mainly by expansion of fields used to produce rice and sugar cane). Only four localities in Senegal, Mali and Mauretania (two rather small oases) are currently known. Of them, the area of Djoudj in the Senegal river delta is the most important, being supposed to host 10% to over 50% of the global population in winter (Flade et al. 2011, Foucher et al. 2013). In 2011, direct communication between wintering grounds and breeding sites of the Aquatic Warblers was

proved for the first time – out of 12 individuals ringed in the inner delta of the Niger river (Mali) in February 2011, one was recovered at the locality of Supoy (Ukraine) at the distance of 5,100 km; of the total of 198 individuals captured in the Djoudj National Park (Senegal) in 2007–2011, one colour-ringed specimen was observed in the Biebrza wetlands (Poland) 5,300 km away (Poluda et al. 2012). France is the most important country on the migration route. An overwhelming majority of the global population seems to pass through this region during the autumn migration and up to 800 individuals are captured there per year (Kerbiriou et al. 2010, Jiguet et al. 2011, Musseau & Herrmann 2013). Julliard et al. (2006) even suppose that during the autumn migration, Aquatic Warblers may move fast from their breeding sites to localities mainly in northeastern France and then continue to their African wintering grounds without making any other stopovers in Europe. However, other important stopover sites are known from Spain, Portugal and Morocco (Neto et al. 2010, Arizaga et al. 2011, Onrubia et al. 2011, Poluda et al. 2012). Most countries with breeding, migrating and wintering Aquatic Warblers as well as a number of conservation institutions have been recently paying major attention to the conservation of this species. At present, the Aquatic Warbler Conservation Team working under the auspices of BirdLife International (www.aquaticwarbler.net) has a leading role in the study and conservation of the species. In the Czech Republic, the Aquatic Warbler ranks among regularly but uncommonly passing species. The analysis of altogether 114 records made in the country till 2007 has shown that the spring passage peaks at the turn of April 3


and May, while during the autumn migration the highest number of birds was recorded in mid September. Findings of nests or records of probable breeding attempts, mainly in central and eastern Bohemia, in southern Moravia and in the Bohemian‑Moravian Highlands are mentioned in a number of publications, however, no convincing evidence of breeding is available (Šťastný et al. 2011). Occurrence of the Aquatic Warbler in the country was relatively numerous at the end of the 19th century and at the beginning of the 20th century (approximately till the 1930s), though. This is documented by repeated observations of several singing males (up to 10) at a single site in spring or several individuals (up to 30) during autumn; occurrence of the species in the breeding season was also quite numerous (Šťastný et al. 2011). The aim of this paper is to analyse available data on occurrence of the Aquatic Warbler in the Czech Republic and to assess its status, as a basis for possible inclusion of the country among range states of the species within the Bonn Convention.

MateriAl and methods For the assessment of occurrence of the Aquatic Warbler, (1) data from the archive and database of the Bird Ringing Centre of the National Museum in Prague, and (2) all known published data on visual observations of this species in the Czech Republic were used. In the analysis, both capture and observation data were classified into three groups: spring migration (1 March – 31 May), breeding season (1 June – 19 July) and autumn migration (20 July – 31 October). However, it is very difficult to define these periods precisely due to a specific life strategy of the Aquatic Warbler (see e.g. de By 1990). In order to evaluate spatial distribution of the records, seven specific regions with occurrence of the Aquatic Warbler were identified within the Czech Republic (see Table 1): – southern Bohemia (south-Bohemian fishpond basins, Tábor and Písek regions), – central Bohemia (the Elbe river basin sensu lato: besides the proper Elbe river basin, sites of a similar charac-

Table 1. Total numbers of Aquatic Warblers (Acrocephalus paludicola) ringed and observed in particular regions of the Czech Republic (see Material), and numbers recorded in particular time periods. Tab. 1. Celkový počet zastižených (kroužkovaných i pozorovaných) rákosníků ostřicových (Acrocephalus paludicola) v jednotlivých oblastech ČR a počty zjištěné v dílčích, zhruba desetiletých (10–14 let) obdobích. region

total

Central Bohemia Boh.-Mor. Highlands Northern Moravia Southern Bohemia Southern Moravia Central Moravia Western Bohemia total

85 41 33 31 21 18 11 240

4

1946–59 1960–69 1970–79 1980–89 1990–99 2000–11 7 5 10 – 9 8 6 45

25 10 2 2 2 4 45

19 1 6 16 1 – – 43

9 2 10 3 5 5 – 34

7 5 2 8 2 3 – 27

18 18 3 2 2 2 1 46

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ter in the Jičín, Česká Lípa, Louny and Kutná Hora regions were also included), – western Bohemia (Plzeň, Domažlice and Karlovy Vary regions), – the Bohemian‑Moravian Highlands, – southern Moravia, – central Moravia (Olomouc, Přerov and Zlín regions), – northern Moravia (Ostrava region and the Odra river basin). Ringing data

number of individuals / počet jedinců

All lists of ringed birds from the years 1934–1998 deposited in the archive of the Bird Ringing Centre of the National Museum, containing small types of rings (2.3–2.5 mm in diameter) of the series M, N, S and Z, used for smaller passerine species, were checked. Data from the year 1999 onward are available in an electronic database. In the archive and database, altogether 143 records of ringed Aquatic Warblers from the period 1948–2011 were found

(Czech Republic 129, Slovakia 14). This is 25 records less compared to the summary data from the annual report on ringed birds (Cepák & Klvaňa 2012) – see Fig. 1. This disproportion may be caused either by a mistake made when counting ringed birds (till 1999 the data were counted manually), by non-provision of ringing data by certain ringers, or by overlooking some data in the ringing lists (several hundreds of thousands of archive records were examined). On the other hand, in some years (1959, 1967, 1976 and 1987) more data were found in the archive than in the summary annual reports. In the ringing lists, the following data are given for each captured individual: ring number, date and locality of the capture, sex and age category, and name of the ringer. For further analysis, only data on individuals captured in the Czech Republic were used (n = 129). The highest number of ringed Aquatic Warblers is available from the years 1961–1980, when altogether 59 speci-

14 12 10 8 6 4 2 0 1934 1939 1944 1949 1954 1959 1964 1969 1974 1979 1984 1989 1994 1999 2004 2009 year / rok

Fig. 1. Numbers of Aquatic Warblers (Acrocephalus paludicola) ringed in 1934–2011 given in annual lists of ringed birds (white columns; n = 168) and those really found in the archive and database of the Bird Ringing Centre of the National Museum in Prague (black columns; n = 143). Obr. 1. Počty okroužkovaných rákosníků ostřicových (Acrocephalus paludicola) z let 1934–2011 uvedených v ročních přehledech kroužkovaných ptáků (bílé sloupce; n = 168) a skutečně nalezená data v archivu a databázi Kroužkovací stanice NM (černé sloupce; n = 143).

5

number of observations / individuals počet pozorování / jedinců


12 10 8 6 4 2 0

1946 1951 1956 1961 1966 1971 1976 1981 1986 1991 1996 2001 2006 year / rok

Fig. 2. Numbers of visual observations (white columns; n = 85) and numbers of observed individuals (black columns; n = 108) of the Aquatic Warbler in the Czech Republic in 1946–2010. Obr. 2. Počty pozorování (bílé sloupce; n = 85) a počty pozorovaných jedinců (černé sloupce; n = 108) rákosníka ostřicového v ČR v letech 1946–2010.

mens were captured, making up 46% of all marked birds. So far no recoveries of the birds ringed in the Czech Republic have been obtained. Visual observations In this case, all known and available published data on occurrence of the Aquatic Warbler in the Czech Republic were used (data included in the archive and database of the Bird Ringing Centre of the NM were omitted). Altogether 85 observations of 108 specimens from the years 1946–2010 were obtained (Fig. 2); 3 specimens were found dead. RESULTS Phenology Ringing data The earliest record of the species is ringing of one specimen on 5 April 1958 (Plzeň); the latest one is the capture of one individual on 1 October 2005 (Žehuň, Nymburk district). Records from the period of spring migration prevail (n = 62), with a peak in the 3rd 6

ten-day period of April. During the autumn migration, altogether 56 individuals were captured with a peak passage in the 1st ten-day period of September (Fig. 3). The capture of 11 birds at the Řežabinec fishpond (Písek district) on 20–21 July 1976 is interesting. It is the earliest summer record in the country, not even excluding possible breeding. Visual observations The earliest observation during spring migration is the occurrence of one individual near Mitrovice in the Šumperk district on 27 March 1988 (Stolarczyk et al. 1994); the latest one is the record of one individual near Rychvald in the Karviná district on 12 October 1952 (Hudec et al. 1966). Data from the period of spring migration prevail again, with 43 observations of 59 birds. During the autumn migration, 19 observations of 24 individuals were made (Fig. 4). Records from the breeding season (1 June–19 July) are interesting, with altogether 22 observations

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25 20 15 10

I/X

III/IX

II/IX

I/IX

II/VIII

III/VIII

I/VIII

III/VII

II/VII

I/VII

III/VI

II/VI

I/VI

III/V

I/V

II/V

I/IV

0

III/IV

5

II/IV


30

10-day period / dekáda

Fig. 3. Occurrence of the Aquatic Warbler in the Czech Republic in 1948–2011, based on ringing data (in particular ten-day periods of April till October; n = 129). Obr. 3. Výskyt rákosníka ostřicového v ČR v letech 1948–2011 na základě kroužkovacích dat (v dekádách dubna až října; n = 129).


16 14 12 10 8 6 4 2 0

10-day period / dekáda

Fig. 4. Occurrence of the Aquatic Warbler in the Czech Republic in 1946–2010, based on visual observations in particular ten-day periods of March till October (white columns – number of observations; black columns – number of individuals). Obr. 4. Výskyt rákosníka ostřicového v ČR v letech 1946–2010 na základě vizuálních pozorování v jednotlivých dekádách března až října (bílé sloupce – počet pozorování; černé sloupce – počet jedinců).

7


160

mean date of spring occurrence průměrné datum jarního výskytu

150 140 130 120 110 100

y = 0,058x + 4,026 R² = 0,019

90 80 1940

1950

1960

1970

1980

1990

2000

2010

2020

year / rok

Fig. 5. Time course of migration of the Aquatic Warbler in the Czech Republic during the spring period of 1948–2011, based on ringing data (1 at the y axis = 1 January; the regression line is ran on mean dates of spring occurrence in particular years). Obr. 5. Průběh tahu rákosníka ostřicového v ČR v jarním období 1948–2011 na základě kroužkovacích dat (1 na ose y = 1. leden; regresní přímka je proložena průměrnými daty jarního výskytu v jednotlivých letech).

mean date of autumn occurrence průměrné datum podzimního výskytu

280 270 260 250 240

y = -0,288x + 805,09 R² = 0,058

230 220 210 200 1950

1960

1970

1980 1990 year / rok

2000

2010

2020

Fig. 6. Time course of migration of the Aquatic Warbler in the Czech Republic during the autumn period of 1956–2011, based on ringing data (1 at the y axis = 1 January; the regression line is ran on mean dates of autumn occurrence in particular years). Obr. 6. Průběh tahu rákosníka ostřicového v ČR v podzimním období 1956–2011 na základě kroužkovacích dat (1 na ose y = 1. leden; regresní přímka je proložena průměrnými daty podzimního výskytu v jednotlivých letech).

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of 25 individuals, all of them singing males. Single birds (n = 66) or two individuals (n = 13) were observed most frequently. Three or more birds were observed in 5 cases only. During the last approximately 60 years (ringing data only), no trend in the timing of spring passage was recorded (b = 0.058, R2 = 0.019, p = 0.28, Fig. 5). A slight tendency to earlier occurrence of the birds can be found during the autumn passage (Fig. 6), however, neither this trend is statistically significant (b = –0.288, R2 = 0.058, p = 0.07). Age and sex Data on age category were available in all captured birds. Most of them (59%) were in the category +1y (i.e. adult individuals) (Fig. 7). In spring, all individuals were determined as adults in the categories +1y, 2y and +2y (n = 62); during the spring passage, 72% juvenile (1y) and 28% adult birds (+1y) were recorded (n = 64). Sex was determined in 20 captured

individuals (17 males, 3 females), only two of them (both males) were captured in autumn. Distribution The Aquatic Warbler was recorded at altogether 89 localities (Appendix 1); spring records come from a larger number of places (n = 61) than the autumn ones (n = 33), during the breeding season the species was recorded at 18 localities (Appendices 2–4). At 6 localities it was found during both spring and autumn migration – Bartošovice (Nový Jičín district), the Zrcadlo fishpond near Mlýnec (Jičín d.), Heřmanský stav (Ostrava d.), the Nesyt fishpond (Břeclav d.), the Nový fishpond near Solec (Mladá Boleslav d.) and the Žehuňský rybník fishpond (Nymburk d.). Concerning the seven regions of the Czech Republic identified in this study, more than a third of the Aquatic Warblers (35%) were ringed or observed in central Bohemia, other 44% of the records come from the Bohemian‑Moravian

31 3 full‐grown 1st year 46

+1st year 2nd years +2nd years

76

Fig. 7. Age of captured Aquatic Warblers (n = 129). Obr. 7. Stáří odchycených rákosníků ostřicových (n = 129). Věk shora dolů: plně vzrostlý, 1. rok, +1. rok, 2. rok, +2. rok.

9


Highlands, northern Moravia and southern Bohemia (Table 1, Appendix 1). Regarding ringing data, the surroundings of Lázně Bohdaneč in the Pardubice district are the most important area, where 19 inds. were captured at the

Sopřečský rybník fishpond (1961–87) and 8 inds. at the Bohdanečský, Tichý and Skříň fishponds (1956–2002). In southern Bohemia, 12 inds. were ringed at the Řežabinec fishpond (Písek d.). The Žehuňský rybník fishpond (Nymburk


70 60 50 40 30 20 10 0

0-200

201-300

301-400

401-500

<500

altitude (in meters) / nadmořská výška (v metrech)

Fig. 8. Numbers of captured Aquatic Warblers in relation to altitude of the locality (n = 129). Obr. 8. Počty odchycených rákosníků ostřicových v závislosti na nadmořské výšce lokality (n = 129).


40 35 30 25 20 15 10 5 0

0-200

201-300

301-400

401-500

<500

altitude (in meters) / nadmořská výška (v metrech)

Fig. 9. Numbers of visual observations (white columns; n = 85) and numbers of observed individuals (black columns; n = 108) of the Aquatic Warbler in relation to altitude of the locality. Obr. 9. Počty pozorování (bílé sloupce; n = 85) a počty pozorovaných jedinců (černé sloupce; n = 108) rákosníka ostřicového v závislosti na nadmořské výšce lokality.

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During the last approximately 40 years, there has been an apparent decline in the number of records in southern Bohemia and at the Moravian localities and, on the other hand, an increase in the number of observations in the Bohemian‑Moravian Highlands and in the last decade also in central Bohemia (Table 1).

d.) was the most frequently visited locality in the last 30 years, with 10 inds. captured in 1990–2011. The distribution of visual observations is quite different – most of them come from the Bohemian‑Moravian Highlands (altogether 38 birds compared to only 3 captured individuals).

ecotone reedbeds/Carex meadows reedbeds ecotone reedbeds/Carex meadows wet meadows reedbeds

22

unknown wet meadows

22

unknown

14

14 78

15

78

15

Fig. 10. Prevailing habitat type at localities where Aquatic Warblers were captured (n = 129). Obr. 10. Typ převládajícího biotopu na lokalitách odchytu rákosníků ostřicových (n = 129). Biotopy shora dolů: rozhraní rákosin a ostřicových luk, rákosiny, podmáčené louky, biotop neznámý.

large‐scale PAs

18

not protected

62

small‐scale PAs

134

Fig. 11. Conservation status of localities with occurrence of the Aquatic Warbler (n = 214). Obr. 11. Ochranný statut lokalit s výskytem rákosníka ostřicového (n = 214). Statut shora dolů: velkoplošná chráněná území, nechráněné lokality, maloplošná chráněná území.

11


Altitude Most of the captured birds came from lower altitudes – 87% of the individuals were captured in lowlands below 400 m a.s.l.; mean altitude of the locality of occurrence was 258 m a.s.l. (range 162–548 m a.s.l.; median = 210 m; n = 129, Fig. 8). In visual observations, mean altitude of the locality was 334 m (170–655 m; median = 240 m; n = 85, Fig. 9). Habitat Majority of the birds were captured in a specific habitat type – in a rather sparse reed stand on the margin of a reed bed or on the margin of a sedge growth (60%), and in wet meadows (11%, Fig. 10). In 12% of the captured birds, only “reed bed” was mentioned as a habitat type, while in the remaining 17% the habitat type could not be identified. Conservation status of the sites More than a half of the individuals (63%) were recorded at sites with no

conservation status, 37% at localities designated as small-scale protected areas (national nature reserves, nature reserves – 29%), protected landscape areas or Special Protection Areas – SPAs (8%, Fig. 11). Changes in numbers Assessment of a long-term trend in numbers of the Aquatic Warbler is difficult due to a significant increase of ringing effort in the Czech Republic in the last 50 years. However, the intensity of ringing effort in wetland habitats (reed beds) can be well expressed using the number of captured Reed Warblers (Acrocephalus scirpaceus) – a common species with more or less stable numbers in the long term (see the Czech Breeding Bird Monitoring Programme 1982–2011, http://jpsp.birds.cz). The increasing number of ringed Reed Warblers (Fig. 12) should thus be a result of higher ringing effort. Despite the apparent increase in this effort,

number of individuals / ind. x 1000 počet jedinců / tisíců jedinců

14 12 10 8 6 4 2 0

1960

1970

1980

1990

2000

2010

year / rok

Fig. 12. Numbers of ringed Aquatic Warblers (Acrocephalus paludicola – dashed line, single specimens) and Reed Warblers (A. scirpaceus – full line, in thousands of specimens) in the years 1960–2011. Obr. 12. Počty odchycených rákosníků ostřicových (Acrocephalus paludicola – přerušovaná čára, jednotlivé exempláře) a rákosníků obecných (A. scirpaceus – plná čára, v tisících exemplářů) v letech 1960–2011.

12

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8

ratio Apal/Asci x 1000 poměr Apal/Asci x 1000

7 6 5 4 3 y = 0,003x² - 10,054x + 10040 R² = 0,446

2 1 0 1960

1970

1980

1990

2000

2010

year / rok

Fig. 13. Relation between the number of captured Aquatic Warblers (Acrocephalus paludicola) and Reed Warblers (A. scirpaceus) in the years 1960–2011. Obr. 13. Poměr počtů odchycených rákosníků ostřicových (Acrocephalus paludicola) a rákosníků obecných (A. scirpaceus) v letech 1960–2011.

the ratio between the number of captured Aquatic Warblers and the number of captured Reed Warblers has declined (Fig. 13). This trend is statistically significant (R2 = 0.446, p < 0.001). DisCUSSION In the last approximately 100 years, the Aquatic Warbler did not rank among common bird species in the Czech Republic. There is no convincing evidence of its breeding, although it cannot be excluded at a few suitable sites (Šťastný et al. 2011). On the other hand, during migration the species occurs in the country regularly, although in small numbers. Relatively numerous records from the breeding season made in the Czech Republic may not indicate possible breeding but can be related to early migration to wintering grounds. The period of migration in the Aquatic Warbler is very difficult to define. De By (1990) differentiated “spring” records (before

30 June) and “autumn” records (after 1 July), mentioning that some males leave their breeding sites already in the last week of June and up to 40% of the females follow them during subsequent two weeks. Most males leave in the second half of July (data from breeding sites in the eastern part of Germany). Migration thus seems to occur in two waves – at first adult males (which do not participate in caring for the young), juveniles from the first breeding attempt and females which did not breed for the second time, followed by the remaining females and juveniles from the second breeding attempt (de By 1990, see also Musseau & Herrmann 2013). The early onset of autumn migration may be also indicated by the timing of fledging of the young at breeding sites in Belarus (Vergeichik 2013) – more than a half of the broods fledge there before late June (53%), especially in the second half of the month (44%), the remaining ones during July and August (32 and 15%, respectively). 13


The time course of spring and autumn migration in the Czech Republic (cf. Figs. 3 and 4) corresponds with the situation in the closest countries with numerous occurrence of Aquatic Warblers (de By 1990). In Germany the spring migration occurred between 20 April and 28 May (median 8 May) and the autum one in the period 7 July – 5 October (27 August); similarly in Switzerland: 6 April – 15 May (28 April) and 20 July – 27 October (with two peaks around 16 August and 25 September), in the Netherlands 9 April – 24 June (6 May) and 5 July – 27 October (15 August). De By (1990) also tried to estimate the ratio between adult and juvenile birds during autumn migration and his data (28.6– 34.5% adult ind.) correspond with the results from the Czech Republic (28%). For a long time, most of the birds were supposed to head westwards north of the Alps during the autumn migration (e.g. de By 1990, Schulze-Hagen 1991). However, birds equipped with geolocators show that at least a part of the warblers from breeding sites in central Ukraine migrate to southwestern France and Spain using the route south of the Alps (Salewski et al. 2013). We can thus suppose that the Czech Republic is situated on the northern migration route and the birds recorded there come probably from breeding sites in northeastern Poland and Belarus (taking into account also the assumed more direct route of spring migration – e.g. de By 1990). The recorded decrease in the number of Aquatic Warblers ringed in the Czech Republic (cf. Fig. 13) is probably connected with the decline of its numbers at breeding sites. It is unlikely that birds from the disappearing Pomeranian population migrate through the Czech Republic, therefore the recorded trend seems to reflect changes in numbers in some of the localities in Poland or Belarus.

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CONCLUSIONS The presented analysis of available records of the Aquatic Warbler provides evidence that the Czech Republic did and still does belong to countries with regular annual occurrence of the species during both spring and autumn migration and with the presence of several important stopover sites, mainly in central and southern Bohemia, in the Bohemian‑Moravian Highlands and in northern Moravia. The Czech Republic thus undoubtedly ranks among range states of the species, defined to cover its European breeding sites, migration corridors or African wintering grounds. Protection of wetland habitats at the important (spring and autumn) stopover sites, used by the Aquatic Warbler during its migration through the Czech Republic, is an essential contribution to conservation of the species. From this point of view, all traditional localities of the species occurrence can be considered important – the Žehuňský rybník fishpond (Nymburk district / National Nature Reserve), Bohdanečské rybníky fishponds (Pardubice d. / a part of a National Nature Reserve) and Řežabinec fishpond (Písek d. / National Nature Reserve), as well as localities where at least two birds were recorded during the breeding season or during migration in the last 20 years (since 1990) – the Jankovský potok stream (Jihlava d. / National Nature Monument), Velký Tisý fishpond (Jindřichův Hradec d. / National Nature Reserve), Tovačovské rybníky fishponds (Přerov d.), Střítežské rybníky fishponds (Jihlava d.), Na Dolňáku wetland near Větrný Jeníkov (Jihlava d.), Frejlach wetland near Horní Cerekev (Pelhřimov d.), Pařezný fishpond near Rudolec (Žďář nad Sázavou d.), Dívčické rybníky fishponds (České Budějovice d.

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/ a part of an SPA), Nový fishpond near Solec (Mladá Boleslav d.), Podvesný fishpond near Pavlov (Žďár nad Sázavou d.), Zrcadlo fishpond near Mlýnec (Jičín d. / SPA) and Havranka near Jiříkov (Havlíčkův Brod / Nature Reserve). Out of the 15 above m entioned localities, eight are designated as small-scale protected areas or Special Protection Areas. Protection or relevant management of suitable habitats should be ensured at least at these localities. At the same time, importance of administrative steps should be stressed. By joining the Memorandum on Understanding Concerning Conservation Measures for the Aquatic Warbler, concluded under the auspices of the Bonn Convention, the Czech Republic would present its willingness to co-operate with other range states in conservation of this globally threatened species and the rarest European passerine in its whole distribution range. Acknowledgements We are obliged to all bird ringers and bird watchers for the effort and attention they paid to the discussed species, and for providing additional detailed information on its ringing and occurrence. We thank two anonymous referees for valuable comments on the manuscript, and Jan Zárybnický and Jan Vrba for preparation of distribution maps. Last but not least we thank Eva Cepáková for the English translation of the article. This work was financially supported by the Ministry of Environment and the Ministry of Culture of the Czech Republic (DKRVO 2013/16, National Museum, 00023272).

Souhrn Studie shrnuje údaje o výskytu rákosníka ostřicového (Acrocephalus paludicola) v České republice v letech 1946–2011. Celkem bylo v tomto období zaznamenáno 129 okroužkovaných jedinců, 85 vizuálních pozorování 108 ptáků a 3 uhynulé exempláře (obr. 1 a 2). U obou skupin dat převažují záznamy z jarního tahu. Ten na základě kroužkovacích údajů vrcholil ve 3. dekádě dubna, na základě pozorovaných ptáků neměl zřetelný vrchol (nejvíce pozorování pocházelo z 1.–3. květnové dekády; obr. 3 a 4). V hnízdním období (1. VI.–19. VII.) nebyl odchycen žádný pták, ale bylo zaznamenáno 22 pozorování 25 jedinců, včetně zpívajících samců. Hnízdění však nebylo doloženo. Podzimní tah probíhal od 3. dekády července s vrcholem výskytu v 1. nebo 2. zářijové dekádě (kroužkovací data, resp. pozorování; obr. 3 a 4). Během zhruba 60 hodnocených let nebyl zjištěn statisticky průkazný trend v načasování jarního ani podzimním tahu (obr. 5 a 6). Rákosník ostřicový byl zjištěn na 89 lokalitách (Příloha 1): jarní a podzimní nálezy pocházely z 61 resp. 33 míst, v hnízdním období byl zastižen na 18 lokalitách (Příloha 2–4). Téměř 80 % nálezů bylo ze středních a jižních Čech, z Českomoravské vrchoviny a severní Moravy (tab. 1). Mezi kroužkovanými ptáky převažovaly adultní exempláře (59 %; obr. 7). Většina byla odchycena v nížinách (průměr = 258 m n. m., medián = 210 m, n = 129), průměrná nadmořská výška záznamů u pozorovaných ptáků dosahovala 334 m (medián = 240 m, n = 85; obr. 8 a 9). Celkem 71 % odchycených ptáků bylo zastiženo ve specifickém typu biotopu – na okraji rákosin s přechodem do nízkých ostřic, nebo na vlhké louce

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(obr. 10). Většina (63 %) pozorovaných a odchycených ptáků byla zjištěna v lokalitách bez územní ochrany, 37 % pak v chráněných územích (obr. 11). Dlouhodobý trend počtu odchycených rákosníků ostřicových vztažený ke kroužkovacímu úsilí naznačuje, že zhruba od roku 1960 dochází ke snižování počtu ptáků protahujících přes naše území (obr. 12 a 13). Předložená analýza nálezů rákosníka ostřicového prokazuje, že Česká republika patřila a stále patří mezi státy s pravidelným každoročním výskytem uvedeného druhu během jarního i podzimního tahu a s přítomností několika důležitých migračních zastávek, především ve středních a jižních Čechách, na Českomoravské vrchovině a na severní Moravě. ČR se tak jednoznačně řadí mezi areálové státy uvedeného druhu, zahrnující jeho evropská hnízdiště, migrační koridory nebo africká zimoviště. Zásadním příspěvkem k ochraně rákosníka ostřicového je zachování mokřadních stanovišť na důležitých (jarních i podzimních) zastávkách jeho migrační cesty přes území ČR. Z tohoto pohledu lze považovat za významné všechny tradiční lokality jeho výskytu – Žehuňský rybník (NB /NPR), Bohdanečské rybníky (PA /část NPR) a rybník Řežabinec (PI /NPR), a dále lokality, na kterých byli v posledních 20 letech (od roku 1990) zastiženi přinejmenším dva ptáci v hnízdním období nebo během migrace – Jankovský potok (JI /NPP), rybník Velký Tisý (JH /NPR), Tovačovské rybníky (PR), Střítežské rybníky (JI), mokřad Na Dolňáku u Větrného Jeníkova (JI), mokřad Frejlach u Horní Cerekve (PE), rybník Pařezný u Rudolce (ZR), Dívčické rybníky (CB /součást PO), rybník Nový u Solce (MB), rybník Podvesný u Pavlova (ZR), rybník Zrcadlo u Mlýnce (JC / PO) a Havranka u Jiříkova (HB /PR). Z 15 uvedených lokalit je plných osm

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chráněno jako maloplošné chráněné území nebo ptačí oblast. Přinejmenším v nich by měla být zajištěna ochrana, příp. odpovídající management vhodných biotopů. Opominout však nelze ani administrativní kroky. Přistoupením k Memorandu o ochraně rákosníka ostřicového, uzavřenému pod záštitou Bonnské konvence, by ČR prezentovala svou ochotu spolupracovat s ostatními areálovými státy při ochraně tohoto globálně ohroženého druhu a nejvzácnějšího evropského pěvce v celém jeho areálu rozšíření.

literature Arbeiter S. & Tegetmeyer C. 2011: Home range and habitat use by Aquatic Warblers Acrocephalus paludicola on their wintering grounds in northwestern Senegal. Acta Ornithologica 46: 117–126. Arizaga J., Mendiburu A., Andueza M., Fon tanilles P., Fourcade J.-M. & Urbina-Tobias P. 2011: Deteriorating weather conditions predict the use of suboptimal stopover sites by Aquatic Warblers Acrocephalus paludicola. Acta Ornithologica 46: 202– 206. AWCT (Aquatic Warbler Conservation Team) 2012: The Aquatic Warbler. www.aquaticwarbler.net (downloaded on 18 Nov 2012). BirdLife International 2012: Acrocephalus paludicola. In: IUCN 2012. IUCN Red List of Threatened Species, ver. 2012.2, www. iucnredlist.org (downloaded on 18 Nov 2012). Cepák J. & Klvaňa P. 2012: Zpráva Kroužkovací stanice Národního muzea za rok 2011. Kroužkovatel 14: 1–24. de By R. A. 1990: Migration of Aquatic Warbler in western Europe. Dutch Birding 12: 165–181. Dézécot J., Le Nevé A. & Bargain B. (eds) 2008: The Aquatic Warbler, a global threatened species. Proc. LIFE seminar “Conservation of the Aquatic Warbler in Brittany”, Bretagne Vivante – SEPNB: 1–120. Dyrcz A. 2006: Aquatic Warbler Acrocephalus paludicola. In: del Hoyo J., Elliott A. &

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Christie D. (eds): Handbook of the birds of the world. Vol. 11. Lynx Edicions, Barcelona: 617. Dyrcz A. & Schulze-Hagen K. 1997: Acrocephalus paludicola, Aquatic Warbler. In: Hagemeijer E. J. M. & Blair M. J. (eds): The EBCC atlas of European breeding birds: their distribution and abundance. T & AD Poyser, London: 564–565. Flade M., Diop I., Haase M., Le Nevé A., Oppel S., Tegetmeyer C., Vogel A. & Salewski V. 2011: Distribution, ecology and threat status of the Aquatic Warblers Acrocephalus paludicola wintering in West Africa. Journal of Ornithology 152 (Suppl. 1): S129–S140. Foucher J., Boucaux M., Giraudot É., André A., Lorrilliére R. & Dugué H. 2013: Nouveaux sites d’hivernage du Phragmite aquatique Acrocephalus paludicola. Ornithos 20: 1–9. Hudec K., Kondělka D. & Novotný I. 1966: Ptactvo Slezska. Slezské museum, Opava. Jiguet F., Chiron F., Dehorter O., Dugué H., Provost P., Musseau R., Guyot G., Latraube F., Fontanilles P., Séchet E., Laignel J., Gruwier X. & Le Nevé A. 2011: How many Aquatic Warblers Acrocephalus paludicola stop over in France during the autumn migration? Acta Ornithologica 46: 135–142. Julliard R., Bargain B., Dubos B. & Jiquet F. 2006: Identifying autumn migration routes for the globally threatened Aquatic Warbler Acrocephalus paludicola. Ibis 148: 735–743. Kerbiriou C., Bargain B., Le Viol I. & Pavoine S. 2010: Diet and fuelling of the globally threatened Aquatic Warbler at autumn migration stopover as compared with two congeners. Animal Conservation 14: 261–270. Kozulin A. & Flade M. 1999: Breeding habitat, abundance and conservation status of the Aquatic Warbler Acrocephalus paludicola in Belarus. Vogelwelt 120: 97–111. Musseau R. & Herrmann V. 2013: Gironde estuary, France: important autumn stopover site for Aquatic Warbler. Dutch Birding 35: 15-23. Neto J. M., Encarnação V. & Fearon P. 2010: Distribution, phenology and condition

of Aquatic Warblers Acrocephalus paludicola migrating through Portugal. Ardeola 57: 181–189. Onrubia A., Ramírez J., Muñoz A.-R., Jubete F., Rguibi H., Zumalacarregiu C. 2011: Identificación de áreas importantes para la migración del carricerín cejudo Acrocephalus paludicola en Marruecos. Resultados de la campaña 2008. Migres 1: 115–119. Poluda A., Flade M., Foucher J., Kiljan G., Tegetmeyer C. & Salewski V. 2012: First confirmed connectivity between breeding sites and wintering areas of the globally threatened Aquatic Warbler Acrocephalus paludicola. Ringing & Migration 27: 57–59. Provost P., Kerbiriou C. & Jiguet F. 2010: Foraging range and habitat use by Aquatic Warblers Acrocephalus paludicola during a fall migration stopover. Acta Ornithologica 45: 173–180. Salewski V., Flade M., Poluda A., Kiljan G., Liechti F., Lisovski S. & Hahn S. 2013: An unknown migration route of the ‘globally threatened’ Aquatic Warbler revealed by geolocators. Journal of Ornithology 154: 549–552. Schulze-Hagen K. 1991: Acrocephalus paludicola (Vieillot 1817) – Seggenrohrsänger. In: Glutz von Blotzheim U. N. & Bauer K. M. (eds): Handbuch der Vögel Mitteleuropas. Band 12/I. AULA-Verlag Wiesbaden: 252–291. Stolarczyk J., Jakubec M. & Hudeček J. 1994: Tah rákosníků ostřicových (Acrocephalus paludicola) ve Slezsku a na severní Moravě. Acrocephalus 15: 22–26. Šťastný K., Bejček V. & Hudec K. 2011: Acrocephalus paludicola (Vieillot, 1817) – rákosník ostřicový. Výskyt v ČR. In: Šťastný K. & Hudec K. (eds): Fauna ČR. Ptáci III/1– 2. 2. přeprac. a dopl. vydání. Academia Praha: 487–488. Tannenberger F., Flade M., Preiksa Z. & Schröder B. 2010: Habitat selection of the globally threatened Aquatic Warbler Acrocephalus paludicola at the western margin of its breeding range and implications for management. Ibis 152: 347–358. Vergeichik L. 2013: Timing when fledglings of Aquatic Warbler leave nests in Belarus. Unpubl. manuscript: 1–5.

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Zadrąg M., Szałanski P. & Lachmann L. 2011: Conserving Aquatic Warblers in Poland and Germany. Achievements of the Aquatic Warbler LIFE project. OTOP Marki, Poland: 1–24.

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Došlo 28. června 2013, přijato 10. září 2013. Received 28 June 2013, accepted 10 September 2013. Editor: P. Procházka

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Appendix 1. List of all records of the Aquatic Warbler (Acrocephalus paludicola) in the Czech Republic in the years 1946–2011. Příloha 1. Souhrnný přehled všech nálezů rákosníka ostřicového (Acrocephalus paludicola) v ČR v letech 1946–2011.

Appendix 2. List of records of the Aquatic Warbler in the Czech Republic during spring migration, i.e. between 1 March and 31 May, in the years 1946–2011. Příloha 2. Přehled nálezů rákosníka ostřicového v ČR v období jarního tahu, tj. od 1. III. do 31. V., v letech 1946–2011.

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Appendix 3. List of records of the Aquatic Warbler during the breeding season, i.e. between 1 June and 19 July, in the years 1946–2011. Příloha 3. Přehled nálezů rákosníka ostřicového v hnízdním období, tj. od 1. VI. do 19. VII., v letech 1946–2011.

Appendix 4. List of records of the Aquatic Warbler in the autumn period, i.e. between 20 July and 31 October, in the years 1946–2011. Příloha 4. Přehled nálezů rákosníka ostřicového v podzimním období, tj. od 20. VII. do 31. X., v letech 1946–2011.

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Status of the globally threatened Aquatic Warbler (Acrocephalus paludicola) in the Czech Republic

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