In 1981-1992, the breeding fauna of 153 fishponds was studies in three fishpond regions in south. Bohemia (Czechoslovakia). On each pond, all water and ...
Hydrobiologia 279/280: 511-519, 1994.
511
J. J. Kerekes (ed.), Aquatic Birds in the Trophic Web of Lakes. © 1994 Kluwer Academic Publishers. Printedin Belgium.
Changes in abundance of water birds species in southern Bohemia (Czech Republic) in the last 10 years Petr Musil & Roman Fuchs 2 Institute of Applied Ecology, Agricultural University of Prague, Kostelec nad Cernymi lesy, CZ-218 63; 2South Bohemian University, Faculty of Biology, Branisovsk6 31, Ceske Budkjovice, CZ-370 05, Czech Republic Key words: fishponds, waterfowl, Anatinae, Podicipediformes, Fulica atra, Galinulla chloropus, Larus ridibundus, Phalacrocoraxcarbo, Cygnus olor, and Anser anser
Abstract In 1981-1992, the breeding fauna of 153 fishponds was studies in three fishpond regions in south Bohemia (Czechoslovakia). On each pond, all water and wetland birds were censused by the Two-check method, which consists of adult birds counts during each breeding season (the first in the second part of May, and the second in the second part of June). We assessed the numbers of all species living in water and wetland habitats in the breeding season. The decline in abundances (expressed as number of individuals) of ducks (Anatinae), grebes (Podicipediformes), Coot (Fulica atra), Moorhen (Galinulla chloropus), Black-headed Gull (Larus
ridibundus) were the most marked changes recorded. Marked increase in abundances was found in Cormorant (Phalacrocoraxcarbo) and Mute Swan (Cygnus olor) during the whole decade, whereas in Graylag Goose (Anser anser) the increase was restricted to the first half of the period under study. Numbers of charadriform and passeriform birds fluctuated in the dependence of water level variation.
Introduction The fishponds and pond systems currently existing in Czech Republic are the result of landscape modification by numerous generations of its inhabitants. Fishponds have been created in suitable places chiefly in Bohemia and Moravia since the 13th century. Intensive development of fishpond management took place mainly during the 15th and 16th centuries. Fish production was the major purpose of creating fishponds. Of course, fishpond management led to the development of shallow and eutrophic water bodies, often overgrown with littoral macrophytes and thus created suitable areas for breeding, resting or migrating waterfowl.
The attention of ornithologists has concentrated on the bird fauna of fishponds since the late 1890s (see e.g. Capek, 1890; Mrazek & Zdobnitzky, 1943). However, more numerous papers on the quantitative composition of bird fauna inhabiting fishponds did not appear until the 1960s, 1970s and 1980s (Havlin, 1967; Hudec, 1975; epa, 1987; Fiala, 1987). Apart from these, many other investigations refer not only to the quantitative and qualitative composition of breeding birds communities on our fishponds, and to requirements of particular species, but also to short and long-term trends in bird numbers. The attention of ornithologists has been focused upon changes in numbers of several water
512 an wetland birds because marked changes observed in particular aquatic and marshland bird species that have been breeding on Czech fishponds since the early 20th century (e.g. Cernk, Hudec, 1977; Stastny et al., 1987). A dramatic change in water birds numbers was noted in the early 1980s. The breeding numbers of the most abundant duck species and some other waterfowl, which has been increasing for several decades, began to decline abruptly in many fishpond regions (Fiala, 1987; Repa, 1987). This declines are different from any other changes in abundances of terrestrial bird species. Our investigations were initiated then in order to obtain missing data, determine the range of these declines, and find possible explanations reveal.
Study area In 1981-82, 1986-87, and 1991 the breeding populations of aquatic birds were censused in 158 fishponds of total area 44,86 km 2 (Table 1) of these fishponds, 123 lie in the Tiebofi Basin Biosphere Reserve, which is one of the largest, oldest and best known fishpond districts of Czech Republic. Twenty one ponds are located in a smaller fishpond region about 20 km north of the Tiebofi Basin in the vicinity of the town of Kardasova Re6ice. The remaining 14 ponds are located in a relatively isolated minor fishpond area about 60 km north of the latter (in the surroundings of the town of Sedl6any).
Methods During the first two research periods (1981-82 and 1986-87) a subset of ponds were studied during the first year, and the remainder during the second year. In 1991, all ponds were censused during the one breeding season. In all ponds under study two checks were carried out during each breeding season, one of them in the second part of May, and the other one in the second part of June (Musil, Fuchs, 1991). On each check all adult birds of the species under study were counted during walking around each pond. We assessed numbers of all species of Podicipediformes, Pelecaniformes, Ciconiiformes, Anseriformes, Ralliformes, Charadriiformes, Lariformes; Alcedo atthis and those species of raptors and Passeriformess which live in aquatic and marsh habitats (see Table 2 for the complete list of the species considerated). In the case of bird species that are difficult to detect or that exhibit territorial behaviour (e.g. passeriform and ralliform birds, some certain charadriiform species) each record of territorial or breeding behaviour was considered to represent the observation of two individuals of the respective species. Two sets of abundance values were obtained for each species under study on each pond. In the case of secluded or territorial species (Tachybaptus ruficollis, Botaurus stellaris, Ixobrychus minutus, Anser anser, Circus aeruginosus, Rallidae,
Charadriiformes, Passeriformes) the higher value
Table 1. Summary characteristics of 158 fishponds under study in 1981-1991. Fishpond characteristic
Minimum
-
maximum
(average)
Total area (km2 ) 2 Water surface area (km ) Littoral stands area (km 2 ) Ratio littoral stands area/total area (%) Length of circumference of water surface (km) Mean water depth (m) Elevation (a.s.l.) (m)
0.0017 0.0012 0.0003 0.86 0.16 0.0 412.0
-
3.9494 3.4000 0.5494 69.90 12.34 2.6 494.0
(0.2970) (0.2559) (0.0412) (21.80) (1.84) (0.66) (441.88)
513 Table 2. Changes in abundances (expressed as a number of observed individuals) and densities (abundance/km 2 ) of particular bird species on 158 ponds under study in 1981-82, 1986-87 and 1991. Species
Podiceps cristatus Podiceps grisegena Podiceps auritus Podiceps nigricollis Tachybaptus ruficollis Phalacrocoraxcarbo Ardea cinerea Ardea purpurea Nycticorax nycticorax Ixobrychus minutus Botaurus stellaris Ciconia ciconia Ciconia nigra Cygnus olor Anser anser Anas platyrhynchos Anas strepera Anas penelope Anas crecca Anas querquedula Anas acuta Anas clypeata Netta rufina Aythya ferina Aythya fuligula Aythya nyroca Bucephala clangula Haliaeetus albicilla Circus aeruginosus
Density (n/km 2 )
Abundance (n) 81, 82
86, 87
576 1
550
563 282
91
81, 82
86, 87
414
12.84 0.02
12.26
9.23
226 250
193 120
12.55 6.29
5.04 5.57
0.02 4.30 2.68
3
120
229
0.07
2.68
5.11
427 2 19 1
456 1 28
464
9.52 0.04 0.42 0.02
10.17 0.02 0.62
10.34
18
81 191 2018 661 39 44 81 26 2156 5866 1 136
33
2 6 3
29
7 9
0.40
141 279 994 502 1 17 31
252 112 1111 807
1.81 4.26 44.99 14.74
3 18
0.87 0.98
31 12 917 1847 82
19 35 894 1747 2 71
1.81 0.58 48.06 130.77 0.02 3.03
2 60
49 48
Rallus aquaticus Porzanaporzana Gallinula chloropus Fulica atra
64 2 89 2985
24 2 58 1464
Vanellus vanellus Charadriushiaticula Charadriusdubius Calidrisalpina Calidris temminckii Calidrisminuta Philomachuspugnax Actitis hypoleucos Tringa glareola
329
87
84
29
3 8 37
2 3
40 1435 252 11 111 1 2 1 3 6 13
0.04 0.13 0.07 3.14 6.22 22.16 11.19 0.02 0.38 0.69 0.02 0.69 0.27 20.44 41.18
91
0.65
0.16 0.20 5.62 2.50 24.77 17.99 0.00 0.07 0.40
1.83
0.42 0.78 19.93 38.95 0.04 1.58
0.74
0.04 1.34
1.09
1.43 0.04 1.98 66.54
0.54 0.04 1.29 32.64
7.33
1.94
1.87
0.65
0.07 0.18 0.82
0.04 0.07
1.07 0.89 31.99 5.62 0.25 2.47 0.02 0.04 0.02 0.07 0.13 0.29
514 Table 2. (Continued) Species
81, 82 Tringa ochropus Tringa nebularia Tringa erytropus Limosa limosa Numenius phaeopus Gallinago gallinago Larus ridibundus Larus minutus Chlidonias niger Sterna hirundo Alcedo atthis Anthus pratensis Motacillaflava Motacilla cinerea Motacilla alba Luscinia svecica Saxicola rubetra Locustella naevia Locustela filuviatillis Locustella luscinioides Acrocephalus schoenobaenus Acrocephalus palustris Acrocephalus scirpaceus Acrocephalus arundinaceus Panurus biarmicus Remiz pendulinus Emberiza schoeniclus Total Number of species
Density (n/km 2 )
Abundance (n) 86, 87
81,82
91 24 3
8
86, 87
0.18
0.54 0.07 0.02
1
18
6
47 16132
10 8235
15 116
17 109
4
5 1 20 8710 1 15 46 3
16 215
9 170
6 34 34 10 1266 290 1028 92
26 42 32 16 938 554 880 84
34 628
146 437
10 10 12 260 36 61 48 20 8 972 440 1228 70 2 104 684
36832 52
19943 51
21312 62
was considered to represent their abundance (i.e. numbers of individuals) whereas in the remaining species an average of both value was used.
Results General trend in species richness and in total waterfowl abundance Altogether 70 species of water and wetland birds were found in the studied area. The species rich-
91
0.40
0.13
1.05 359.63
0.22 183.58
0.33 2.59
0.38 2.43
0.09
0.11 0.02 0.45 194.17 0.02 0.33 1.03 0.07
0.36 4.79
0.20 3.79
0.13 0.76 0.76 0.22 28.22 6.46 22.92 2.05
0.58 0.94 0.71 0.36 20.91 12.35 19.62 1.87
0.76 14.00
3.25 9.74
0.22 0.22 0.27 5.80 0.80 1.36 1.07 0.45 0.18 21.67 9.81 27.38 1.56 0.04 2.32 15.25
821.10 52
444.59 51
475.11 63
ness in 1991 was considerably higher than species richness in preceding years. Among species newly recorded in 1991 waders were predominantly represented. Being obviously late migrants, their occurrence on studied ponds is presumably a consequence of draining of ponds due to harvesting the fish stock. Changes in total abundance (e.g. total numbers of individuals) of observed bird species corresponded to changes in numbers of main waterfowl group (Lariformes, Anseriformes, Gruiformes, Podicipediformes - see Fig. l a and b).
515 ,, -*%j
others Passeriformes 30- ---
u)
Lariformes
'1
Gruiformes ._
u) .i
20- --
Anseriformes
o
I-
Podicipediformes
E 10- --
0- --
l1~
86-87 years
91
.1 ^rn 1 IIL J~S -V
Charadriiformes 1000-
Falconiformes
m-
Ciconiiformes
a
750-
m-
Pelecaniformes
'4-:I-
a
500- ---
E c:
250-
0- b------
81-82
86-87 years
91
Fig. 1. A. Changes in total abundances of main waterfowl group. B. Changes in total abundances of rarer waterfowl groups (in Fig. 2a marked as others).
516 Total abundances of Charadriformes, Passeriformes and Falconiformes did not corresponded to this trend. The total abundance of Pelecani-
pond regions of former Czechoslovakia (Fiala, 1987, Repa, 1987). This reduction came to a halt in the second half of the 1980s, and, (Anas strep-
formes, represented only by Phalacrocoraxcarbo,
era, Netta rufina) abundances of some species
increased markedly during the period under study.
began to increase again. However, the decline in abundances has not been satisfactorily explained so far. In many fishpond regions in former Czechoslovakia, an increasing of mortality was recorded in many aquatic birds (most frequently due to botulism) between 1975-1983 (Hudec et al., 1984). Similarly, massive loss-rates due to botulism were reported from some others central European countries in 1981-83 (Reichholf, 1983, 1985). A significant decline in the reproductive capacity (i.e. clutch size, brood size, numbers of breeding pairs and their ratio to the total numbers of duck populations) was observed in most ducks and other waterfowl species in the 1980s (Kloubec & Svecova, 1990; Musil, 1990). Decreasing abundances of some duck species
Changes in abundances of particular water and wetland species
The changes in the numbers of particular aquatic and marshland bird species in our study area in the course of the 1980s are summarized in Table 2. Abundances of 4 species (Anas crecca, Anas querquedula, Anas clypeata, Gallinula chloropus)
was declined markedly during the whole 1980s. Abundances of 9 species (Podicepsnigricollis,Anas platyrhynchos, Aythya ferina, Aythya fuligula, Bucephala clangula,Fulica atra, Larus ridibundus,Acrocephalusschoenobaenus)declined markedly only
in the first half of studied period and abundances of other 5 species (Podiceps cristatus, Tachybaptus ruficollis, Sterna hirundo, Locustellafiuviatillis)only
in the second half of 1980s. The abundances of 4 species were increasing considerably in the course of whole 1980s (Phalacrocorax carbo, Saxicola rubetra, Cygnus olor, Ciconia nigra) and abundances of 2 species (Nycticorax nycticorax, Locustella naevia) increased
markedly only in the first half of 1980s. In other species, no marked trends in abundance were recorded or, if any, they were found only in small numbers of individuals.
(Anas platyrhynchos, Anas strepera, Aythya ferina,
Aythyafuligula) can be partly explained by gradual coverage of islets, which are optimal breeding habitats for a number of duck species (Stastny et al., 1987b) by shrubs and trees. The decline in abundances of some other duck species (Anas crecca, Anas querquedula, Anas clypeata) can by
explained by draining and ploughing of meadows adjacent to the fishponds, and by bulldozing the littoral vegetation (Bejcek et al., 1990), and thus by destruction of their breeding habitats. Furthermore it is possible to expect a negative effect of gradually increasing fish stock size, which would result into the competition between fish and some waterfowl, e.g. ducks (Pykal, personal communication).
Discussion Ducks, grebes, coots and gulls
Cormorant
The decline in the numbers of all duck species as well as in many other aquatic bird species (e.g.
The most marked increase in numbers (see Table 2) was recorded in Cormorant (Phalacrocorax carbo), which is consistent with an increase of this species populations within whole Europe (e.g. Cramp & Simmons, 1986; Sellers, 1989; Suter, 1989; Menke, 1989; Aubrecht, 1991, etc.).
Podicepssp., Fulica atra, Gallinula chloropus, Larus
ridibundus) during the first half of the 1980s is obviously the most important change recorded. Similar decline has been observed in many fish-
517 The first breeding colony rose in our study areas (and also in Bohemia) in 1983 (see Musil et al., 1993 for datail on its development).
Mute Swan & Greylag Goose Numbers of breeding pairs of both these species in south Bohemia was a continually increasing for several decades (Hora, 1989; Simek, 1991). The increase of Mute Swan (Cygnus olor) abundance continued the second half the 1980s (see Table 2), being thus consistent with an expansion of this species in Czech Republic (Stastny et al., 1987, Stastny & Bejcek, 1989; Hora, 1989). Increasing abundance of Greylag Goose (Anser anser) came to a halt in the half of the 1980s, and then began to decrease (see Table 2.), which may be presumably considered as a consequence of repeated dewatering of many fishponds in breeding season (Simek, 1991).
Waders The numbers of most waders depend, to a considerable extent, on the decrease of water due to dewatering of ponds in order to harvest the fish stock. Dewatering ponds are preferred by waders breeding on ponds (Vanellus vanellus, Charadrius dubius), on in their vicinity (Tringa ochropus) and also by spring migrating waders (Actitis hypoleucos, Philomachus pugnax, Tringa glareola, and other waders species - see Table 2). The decline in abundances of waders species, which breed in meadows and wetlands (Tringa totanus, Limosa limosa, Gallinago gallinago), has been continuing already for several decades as a consequence of the agricultural changes mentioned above (Salek, 1987; Stastny et al., 1987a).
usually negative affected by dewatering of ponds due to harvesting the fish stock, which might have coincided with the their breeding season in several last years. The differences in abundance changes of particular Passeriform birds, can be explained by different requirements (e.g. Chatchpole, 1972; Leisler, 1981) of these species for the magnitude of flooding of littoral stands. The decrease was therefore recorded in those species that are more dependent on habitats in which the macrophytes are flooded (Acrocephalus schoenobaenus, Acrocephalus arundinaceus, Locustella luscinioides) whereas in those dependent on littoral stands only little or not at all (Acrocephalus scirpaceus,Emberiza schoeniclus, Saxicola rubetra, Luscinia svecica) no declines in abundances were found.
Importance of changes in species abundances in the study area In evaluating the trends of the development of numbers of several bird species, the fact must be taken into account that Czech Republic lies at the northern limit of the breeding range of some bird species (e.g. Ardea purpurea, Nycticorax nycticorax, Netta rufina) or, on the contrary, at its southern edge (e.g. Aythyafuligula, Bucephala clangula, Tringa ochropus). Consequently, one may expect a greater variation in numbers of breeding pairs here than in the centres of their respective ranges (Cramp & Simmons, 1986, 1987). Furthermore, one should also consider the period fact that even during the period of the greatest decline in breeding numbers, the densities (see Table 2) of many species in our study areas were many times higher than those observed in other parts of their respective breeding ranges (see e.g. Kjellen, 1978; Haapanen & Nilsson, 1979; Thomas, 1980; Poysa, 1983; Koskimies & Poysa, 1989).
Passeriformes
Conclusion The majority of Passeriform birds depend strongly on littoral stands, i.e. on their breeding habitats. Hence the are Passeriform birds are
In 1981-1991, the breeding fauna of 153 fishponds was studied in three fishpond regions in
518 south Bohemia (Czech Republic). On each pond, all water and wetland birds were censused by the Two-check method (Musil & Fuchs, 1991), which consists of two adult birds counts during each breeding season (one of them in the second part of May, and the other one in the second part of June). We assessed the abundances (i.e. numbers of individuals) of all species living in water and wetland habitats in the breeding season. The decline in abundances (expressed as number of individuals) of ducks (Anatinae), grebes (Podicipediformes), Coot (Fulica atra), Moorhen (Galinulla chloropus), Black-headed Gull (Larus
ridibundus) were the most marked changes recorded. Marked increase in abundances was found in Cormorant (Phalacrocorax carbo) and
Mute Swan (Cygnus olor) during the whole decade, whereas in Graylag Goose (Anser anser) the increase was restricted to the first half of the period under study. Numbers of charadriform and passeriform birds fluctuated in the dependence on water level variation.
Acknowledgements This study could have been conducted to the field terrain work of almost 20 ornithologists, which participated on the field census. Our thank are also due to Dr Joseph J. Kerekes for his kindness making possible to present our results at Aquatic Birds Symposium' 1991 in Sackville and to Petr PySek for improving our English. References Aubrecht, G., 1991. Historische verbreitung und aktuelle Brutversuche der Kormorans in Osterrreich. Vogelschutz in Osterreich 6: 44-47. Bej6ek, V., A. Exnerovi, R. Fuchs, P. Musil, L. Simek, K. Stastnr, P. VaSik, 1990. Zmeny po6etnosti jednotlivych druhfi vodnich ptfkfi na vybranych rybnicich Tfebofisk6 panve - srovnani let 1981, 1982 a 1986, 1987. Ptaci v kulturni krajine, Sbornik referatu, Ceske Budejovice: 1724.
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