The Bulgarian Ornithofauna

Tanyu Michev and Petar Iankov

Summary

This report presents a brief review of the history of ornithology in Bulgaria. Several stages in its development are described. The contributions of Bulgarian and foreign scientists to our knowledge of the Bulgarian birds are noted, as are the important publications (e.g., Reiser, 1894; Patev, 1950; Simeonov et al., 1990; Simeonov and Michev, 1991).

The second part of this report describes major gaps in knowledge and research needs. The species composition of the Bulgarian birds is well known, but subspecies affiliations of the birds in several orders have been insufficiently studied. The delineation of ornithogeographical provinces of the country is incomplete. Establishment of ornithogeographical districts will be possible only after full regional investigation of the Bulgarian territory. The birds of many large areas - the Danubian plain, the mountains near the border with Serbia and Macedonia (excepting the Stara Planina and Ograzhden), the Rila Mountains, the western Rhodope Mountains - have not been well investigated. Certain biological characteristics (feeding and food habits; eggs shapes, sizes, and colors; incubation periods; hatching; molting periods, etc.) of the majority of the Bulgarian birds are insufficiently studied. Full inventory of the birds of the protected areas has not yet begun. The emphasis in future studies should be on the preparation of the "Atlas of the Breeding Distribution of the Bulgarian Birds." Investigations of the influence of agricultural changes on the Bulgarian avifauna are essential. Research should also be undertaken to derive solutions to several current problems (e.g., conflicts between birds and fish farms, between birds and aviation, and between birds and powerlines).

The third part of this report provides a current assessment of the Bulgarian avifauna according to 10 criteria:

1. Poorly known geographic regions. Eleven geographic regions where the species composition of the birds has been insufficiently studied are identified. The largest of these is the Danubian Plain; the smallest is Bakadzhicite.

2. Species richness. The number of established species, the number of breeding species, the area (if data are available), and the sources of information for 22 geographic regions are presented. The number of species is greatest in the eastern Rhodope Mountains, where in an area of 6005 km2 258 species of birds have been established. Of these, 167 are breeding species.

3. Rare species. Sixteen species are accepted as globally threatened, and 61 rare and threatened bird species from the Bulgarian Red Data Book are noted. Unpublished information (including information from the Atlas of European Breeding Birds was also used. Rare species are most concentrated in the region of the Bourgas Lakes.

4. Endemism. Endemism has not been established for any members of the Bulgarian ornithofauna.

5. Unique ecosystems, habitats, and communities. Two globally significant sites are discussed: Pirin National Park and the Srebarna Nature Reserve. The region of Durankulak and Shabla, where almost all of the world's population of the red-breasted goose (Branta ruficollis) winters, is also of global importance. Several other geographical regions of European and national importance are noted.

6. Ecological services. The Via Pontica - one of the largest and most important bird migration routes in Europe - and other smaller migratory routes are de-scribed. The main winter waterfowl concentration points (Shabla, Durankulak, the Bourgas lakes, Ovtcharitsa reservoir) are also noted.

7/8. Fragility and threats. These are depicted together on a single map. The authors regarded wetland ecosystems as the most threatened and fragile ecosystem type, followed by the alpine parts of the high mountains. Several known threats (direct persecution, habitat destruction, etc.) are pointed out.

9. Sites containing the most representative samples of Bulgaria`s biodiversity. This list was prepared on the basis of 15 habitat types according to the classification proposed in the CORINE Biotope Project. Habitat types are represented by different colors on the applied map.

10. Species of proven or potential economic importance. The white-fronted goose, cormorant, starling, and white stork are included in this group of species.

Past, current, and potential threats to the survival of the biota are described in the fourth part of the report. Current and potential menaces are emphasized.

Proposals for the conservation of the Bulgarian avifauna are offered in the report's conclusion. The discrepancy between the existing protected areas (which are concentrated in the high mountains) and relatively low-elevation but species-rich areas is pointed out. The authors recommend that scientific studies be intensified due to accelerated rates of degradation and the loss of Bulgarian faunal integrity.

A Brief History of Ornithology in Bulgaria

Bulgaria's avifauna has long been of the utmost interest. This is due to the fact that Bulgaria, with its special central location in the Western Palearctic region and the Balkan Peninsula, includes parts of four biogeographical provinces (according to Udvardy`s 1975 classification). This is a rare phenomenon for a country with such a small (111,000 km2) territory.

Scraps of information about Bulgaria's birds have come down to us in the works of the writers and naturalists of antiquity. Some data about the more ordinary bird species in Bulgaria can be found in Old Bulgarian literature. The pastoral eulogy of the creation in John the Exarch`s Hexameron mentions about ten species of birds. More exact data have been found in the descriptions of travellers during the Renaissance.

The information on birds contained in the fifth volume of the six-volume work by Conte Luigi Fernando de Marsilli (1650-1730), founder of the Academy of Sciences in Bologna, proved to be the earliest of real scientific importance. This volume, published in 1726, is entitled A Description of the Danube from Kalenberg Mountain in Austria to the Mouth of River Jantra. One of the earliest explorers of nature of Bulgaria, the Hungarian scientist-academician Emerich (Imre) von Friwaldsky (1779-1874), organized four natural history expeditions in Bulgaria, and took part himself in two of them. He provided data on certain species of birds found in the foothills of the Rhodopes near the town of Stanimaka (now Assenovgrad), and in 1838, using a specimen found in Plovdiv, described the turtle dove as a species new to science.

From the second half of the 19th century on, foreign ornithologists who had visited certain parts of Bulgaria or who travelled throughout the country regularly published their findings. The first attempt at a more thorough study of the Bulgarian avifauna was made by O. Finsch, who in 1859 published data on the distribution of 178 bird species. Papers by many authors (E. Hodek, C. Farman, H. J. Elwes, T. E. Buckley, L. Lorenz-Liburnau, W. N. Radakoff, L. Kalbermatten, E. F. Homeyer, and G. Sintenis) appeared in this period. The great contributions made by Georgi Christovich (1863-1926), the first Bulgarian ornithologist, should be pointed out. At the time he was in charge of the natural history collections of the Higher School in Sofia (now Sofia University "St. Kliment Ohridski"). He was the founder of the first ornithological collection and author of 150 articles on our fauna.

Dr. Othmar Reiser (1861-1936), curator of the museum in Sarajevo, had special significance not only to Bulgarian but to Balkan ornithology. He published a four-volume series Materialen zu einer Ornis Balcanica, the second volume of which was devoted entirely to the birds of Bulgaria. This volume was used by Dr. E. Klein in writing his popular science book Our Birds (1909).

During the first half of the 20th century, ornithological studies were undertaken in Bulgaria by V. Varbanov, V. Vlaskov, K. Kuzev, V. Kovachev, A. Petrov, N. Radev, I. Sokachev, P. Drenski, and V. Strybrni, and by the foreign ornithologists K. Andersen, H. Boetticher, D. Gengler, A. Jordan, B. Rensch, H. Schumann, G. Wallis, A. Wolf and many others.

The Bulgarian Bird Banding Centre was founded in 1928. Its first director was Pavel Patev (1889-1950), who was engaged in bird banding and other research work. He wrote the monograph "Birds of Bulgaria" on the basis of data from the literature and his own studies. This monograph became the vade mecum for generations of ornithologists. Paralleling his research work, he engaged in wide-ranging activities as a member of the Union for the Protection of Nature for the preservation and protection of birds. In 1940, on his initiative, Srebarna Lake was proclaimed Bulgaria's first bird refuge.

Nikolaj Boev (1922-1985) continued the work of Patev. He worked at the Zoological Garden in Sofia, at the Institute of Zoology of the Bulgarian Academy of Sciences, and at the Research and Coordinating Centre of Ecology and Environmental Protection. He undertook broad scientific research and environmental work not only as regards birds, but the entire spectrum of biodiversity in the country. It was his idea to compile the Bulgarian Red Data Book.

In the last 20 to 30 years ornithological studies in Bulgaria have become better planned, more purposeful, and better supported with finances, equipment, and staff. Ornithological research is now performed by the Institutes of Zoology and Ecology of the Bulgarian Academy of Sciences, the Faculty of Biology at Sofia University, the Forestry Institute, Plovdiv University, the Museums of Natural History in Plovdiv, Kotel, and Srebarna, and the natural history departments of the museums in Bourgas, Varna, Pleven, Russe, Belogradchik, Dobrich, and Blagoevgrad, among others. Research work is also assisted by hundreds of amateurs, many of whom are members of the Bulgarian Society for the Protection of Birds, and the Bulgarian Ornitho-Centre. Publication of a "Bulletin of Ornithological Information" has recently begun, and long-term stationary research has been initiated at the biosphere reserves of Srebarna, Rupite, and Atanassovsko Lakes.

Additions to the ornithological collection of specimens, eggs, and nests at the National Museum of Natural History are constantly made. This is the oldest collection in the Balkan Peninsula and contains more than 10,000 eggs from about 1,000 bird species (approximately 1/9 of the world's avifauna).

In recent decades, a number of important ongoing ornithological projects have been undertaken, some of which still continue:

During the last few years several primary ornithological works have been published, including Volume 1 of the Fauna of Bulgaria: Aves (Volume 2 is being prepared and work on Volume 3 is ongoing) and the Field Guide of the Birds of the Balkan Peninsula (a Peterson-type guide). Some new trends and methods in Bulgarian ornithology (urban ornithology, radar-ornithology, paleo-ornithology, marking with colored bands, etc.) have been initiated. An especially positive trend is the significant increase in the number of bird watchers in Bulgaria. All of these shall contribute to the realization of the "Atlas of the Breeding Distribution of Bulgarian Birds," based on a 10 km2 grid format. These trends also hold promise for the more effective protection of Bulgaria's avifauna.

Gaps in Knowledge

Despite the fact that species of birds new for Bulgaria are found almost every year, the species composition of the Bulgarian avifauna is well explored. However, the situation with bird subspecies is not the same. This gap in our knowledge is especially important in terms of bird that migrate across or winter in Bulgaria. They belong mostly to the orders Passeriformes or Charadriiformes. The lack of data about subspecies is due to the fact that biometrical and morphological studies have not kept abreast with other areas of ornithological study. This is why, for example, data about body sizes, weight, and other morphological features are still taken from foreign sources.

We have not yet been able to divide our territory into ornitho-geographical regions or districts, despite the serious attempt of Georgiev and Simeonov (1992) to do so. It will be possible to solve this problem only as the gaps in the regional investigations of the Bulgarian territory fill up. The species composition of the birds of many large geographical regions - the Danubian plain, the mountains along our western border (except the Stara Planina and Ograzhden), Belasitsa, Slavyanka, the western Rhodopes and Rila Mountains) - has not been completely investigated. Some of the regional studies (such as those of the Stara Planina and Pirin Mountains) were conducted decades ago and must therefore be updated.

For the majority of Bulgarian birds, a number of biological characteristics (feeding and food habits; egg shapes, sizes, and colors; incubation periods; hatching; molting periods, manner, and places, etc.) are incompletely or insufficiently studied. Systematic and complete information about the periods, character, and migration routes of the migrating birds is lacking. Information on the concentration points and staging areas of birds during migration periods is also insufficient. Despite the increased number of birds banded in Bulgaria during recent years, the wintering sites of the Bulgarian birds are poorly known. Data about the negative factors that affect bird populations at on their wintering grounds are scarce. For example, only when most of the Dalmatian pelicans of the Srebarna reserve were banded with colored plastic bands was it established that they over-winter in Porto Lago (northern Greece). It was further discovered that many of them perish as a result of collisions with a power transmission line that is located between their roosting and feeding places.

An inventory of the avifauna of all natural reserves, national parks, and other protected areas has not yet begun. There is no information about trends in the population numbers, nesting success, or the negative factors that influence bird populations in the protected areas. Answers are lacking for two basic questions: 1) Does the Bulgarian network of protected areas cover the needs of the birds, and if so to what degree? 2) What changes or additions to the network should be made to make it more effective for the protection of the birds? There are no serious studies of the population dynamics, ecological requirements, and influence of anthropogenic factors on the birds included in the Bulgarian Red Data Book. The influence on the birds of heavy metals, artificial fertilizers, and different chemical substances (herbicides, insecticides, toxic wastes, etc.), and of oil pollution in the water basins, is incompletely studied. The possibilities for cooperation in protecting birds that sojourn in Africa, the Orient, and the Middle East after their breeding period have not been investigated.

Research Needs

Changes in economics and agriculture have created a need for correct information on the winter and summer distribution of the birds over the whole territory of Bulgaria, i.e. for an "Atlas of the Breeding Distribution of the Birds in Bulgaria" and an "Atlas of the Winter Distribution of the Birds in Bulgaria." Some European countries have published second editions of such atlases, while others have completed winter atlases; Bulgaria, in the meantime, has fallen behind. Such atlases provide a substantial basis for tracing changes in species composition over long periods of time. They aid in the correct determination of threatened, vulnerable, and rare bird species. They would undoubtedly help to distinguish the ornitho-geographical regions or districts of our country.

Compiling this information would require the organization of a Center for Biological Information. In this center, all information on the distribution and numbers of species should be collected, elaborated, and published. The compiling of a Bulgarian atlas of breeding birds should be facilitated by the recent publication of the Field Guide of the Birds of the Balkan Peninsula and by the establishment of the Bulgarian Society for the Protection of Birds (BSPB). A plan to undertake this work has been organized within the BSPB and it will probably produce the atlas.

The effect on the avifauna of changes in agricultural policies and practices (especially changes in field sizes and cropping patterns) needs to be examined. For example, we know that virtually the entire population of the red-breasted goose over-winters in South Dobrudzha and feeds in vast sown fields. We do not know whether this species will keep the same wintering site under changing land uses and what measures are needed to guarantee its survival. At the same time, the problem of crop damage by the red-breasted goose needs to be addressed.

Ten years have passed since information for the Red Data Book was collected. It is very important to check breeding habitats to determine trends in the numbers of every species, to review current protection measures, and to plan new initiatives. New species status categories need to be devised and brought into closer agreement with international categories.

Research on mid-winter numbers of waterfowl and on the autumn migration of soaring birds along the Black Sea coast (a special form of monitoring of many species, including rare and threatened species from eastern Europe) should continue.

Another area of investigation ought to involve the influence of artificial fertilizers, heavy metals, pesticides, and other chemical substances on the Bulgarian avifauna. The first issue that should be addressed is the extent to which the Bulgarian birds have been harmed by these substances.

Solutions to several practical problems also need to be addressed. These include the conflicts between birds and fish-farms, aviation, agriculture (including the problem of the damage caused by the more than 150,000 wintering geese), apiculture, and power transmission lines.

Biometrical, morphological, ecological, zoological, nidological, ornithocenological, and ornithogeographical investigations need to be more fully developed in the future.

Current Assessment

The assessments presented here are based on published scientific information and on data and observations collected by the authors during tours throughout Bulgaria. The personal communications of Bulgarian and foreign ornithologists, both professionals and amateurs, have also been used.

Areas Requiring Further Study

The territories listed below have been designated as "poorly known geographic areas." Although there is scientific information about these areas, it is scarce, fragmentary, outdated, and unreliable, and so was not used for the purposes of this report.

1. The Danubian plain. Located along the Danube's shore, the Stara Planina Mountains, and Ludogorie. Its area, together with south Dobrudzha and Ludogorie (except the Danube shore), is 28,523 km2. This region has been heavily influenced by human activity. Virtually the entire area consists of agricultural lands. "Wild nature" exists only in several valleys of the rivers that cross the plain (Iskar, Vit, Ossam, Yantra, Russenski Lom, Tchernzhalka). Medium species richness.

2. Kraischteto. Historical geographic area in Serbia and Bulgaria, located among Znepole, Radomirska Kotlovina, the valley of the Strouma River, Kjostendilska, Kamenischka Kotlovina, and the valley of Morava River. In the Bulgarian territory it includes the following mountains: Karvav kamak, Milevska planina, Zemenska planina, Rudinite, Stranzha and Tcherna gora. It is covered by sparse deciduous and coniferous forests and is sparsely populated. Medium species richness.

3. Verila Mountain. A mountain in the western part of Bulgaria, with orographical connections to the mountains of Rila and Vitosha. Its highest point is at 1450 m above sea level (a.s.l.). Covered with sparse deciduous forests except for its deforested southwest part. Low species richness.

4. Rila Mountains. The highest mountain group of Bulgaria and the Balkan Peninsula (2925 m a.s.l.). Its area is 2629 km2. The Rilas are rich in coniferous forests (consisting predominantly of Pinus and Picea). Small areas are covered by Fagus forests. There are 223 alpine lakes. High species richness.

5. Maleshevska Planina. A mountain of the Osogovsko-Belasishka mountain group. Its ridgeline serves as the border with Macedonia. Its highest point is at 1803 m a.s.l. Forests of Fagus and Quercus daleschampii predominate. Medium species richness.

6. Belasitsa. A mountain in the southwestern part of Bulgaria. Its ridgeline serves as the border with Greece and Macedonia. The highest point is at 2029 m a.s.l. Fagus forests predominate and at lower elevations are mixed with Acer pseudoplatanus, Platanus orientalis, and Castanea sativa. Medium species richness.

7. Slavyanka. A mountain in the southwestern part of Bulgaria. Its ridgeline serves as the border with Greece. The highest point is at 2212 m a.s.l. Most of the mountain's area is beyond the territory of Bulgaria. Forests of Quercus, Fagus, and Pinus heldreichii predominate. High species richness.

8. Western Rhodope Mountains. The western part of the Rhodopes, the highest point of which is at 2191 m a.s.l. A portion of this area is in Greece. Coniferous forests of Picea abies, Pinus silvestris, and P. nigra predominate. Deciduous forests of Fagus, Quercus, and Carpinus also occur. High species richness.

9. Hills of St. Ilija and Monastery Hills. These hills are located between the small rivers of Blatnitsa and Tundzha. Their highest points are at 416 and 600 m a.s.l. respectively. The highest areas are covered with deciduous forest. Medium species richness.

10. Bakadzhicite. A hill located southwest of the town of Yambol. Its highest point is at 515 m a.s.l. Deforested. Low species richness.

11. Sakhar Planina. A mountain located along the Maritsa, Sazlijska, and Tundzha Rivers. The highest point is at 856 m a.s.l. It is covered by sparse deciduous forest. Medium species richness.

Species Richness

We here use "species richness" in the sense of "number of species." The best, most accurate, and latest estimates from the Bulgarian ornithological sources have been used. Two options were available in determining species richness: using the total number of established birds or the number of breeding species only. We accepted the second option. The same approach was used by Simeonov and Georgiev (1992) in describing the zoogeographical characteristics of the Bulgarian avifauna. Numbers for both, however, are provided in the text that follows. The first is the total number of species occurring in a given area; the second is the number of breeding species.

The classification of groups as proposed in the instructions to the authors is not suitable for characterizing the regions with different species richness in Bulgaria. The proposed classification would have allowed us to mention only two groups - those areas with 10-100 species and those areas with 100-500 species. We adopted the following grouping system (and the following colors for the applied map, Map 20, p.):

Green: 50-99 species
Violet: 100-149 species
Red: 150-199 species
Black: 200-249 species
Blue: poorly known areas

Determination of species richness was made bearing in mind several potential sources of error. The elapsed time between the oldest (Petrov and Zlatanov, 1955) and most recent (Milchev, 1991) publications used is 36 years. Some authors did not provide information on the exact borders and area of their study sites. Finally, the borderlines were plotted on small-scale maps instead of standard topographical maps, and thus are inexact.

Species richness of the different geographic regions is as follows:

1. Danube shore. 3500 km2 with 122/103 species (Paspaleva-Antonova, 1961).

2. Srebarna Natural Reserve. 600 ha with 162/103 species (Michev, 1968a).

3. Russenski Lom National Park. 2227 ha with 110/81 species (Profirov and Undjijan, 1985).

4. Ludogorie. 194/54 species (Simeonov, 1975).

5. South Dobrudzha. 203/96 species (Petrov and Zlatanov, 1955).

6. Varna District. 236/136 species (Peshev, 1971).

7. Western Stara Planina Mountains. 201/145 species (Donchev, 1970).

7a. Iskar Gorge (Iskarski Prolom). 132/78 species (Simeonov, 1967).

7b. Valley of Botevgrad (Botevgradska Kotlovina). 172/112 species (Simeonov et al., 1984).

8. Central and Eastern Stara Planina Mountains. 230/152 species (Donchev, 1971).

8a. Boatin Natural Reserve. 1228 ha with ?/80 species (Spiridonov et al., 1983).

8b. Tzaritchina Natural Reserve. 1420 ha with 134/57 species (Spiridonov et al., 1983).

9. The Rose Valley. About 1000 km2 with 232/128 species (Donchev, 1977).

10. Lyulin Mountain. 137/96 species (Georgiev, 1989).

11. Town of Sofia. 181 km2 with 243/106 species (Iankov, 1983a).

12. Vitosha Mountain. 278 km2 with 114/96 species (Donchev, 1961).

13. Plana Mountain. 99/72 species (Sufi, 1990).

14. Mountains of Sredna Gora. 5950 km2 with 230/152 species (Petrov, 1981).

14a. Lozenska Mountain. 127/65 species (Dimitrov, 1991).

15. Bourgas District. 269/141 species (Prostov, 1964).

15a. Atanassovsko Lake Natural Reserve. 1050 ha with 214/38 species (Roberts, 1985).

16. Strandzha Mountain. 2950 km2 with 273/147 species (Milchev, 1991).

17. Konyavska Mountain. 178/109 species (Simeonov and Delov, 1989).

18. Osogovska Mountain. 126/108 species (Marinov, 1989).

19. Trakia. 248/127 species (Boev et al., 1964).

20. Ograzhden Mountain. 166/109 species (Simeonov and Baeva, 1988).

21. Pirin Mountains. 2585 km2 with 217/156 species (Simeonov, 1986).

22. Eastern Rhodope Mountains. 6005 km2 with 258/167 species (Iankov, 1991b).

Analysis shows that species richness within the territory of Bulgaria is lowest in northern Bulgaria and highest in the southern parts of the country. The highest total number of resident, migrating, and wintering birds is found at Strandzha Mountain area (273 species, as compared with a total of 383 reported for the whole of Bulgaria).

The overview of species richness in Bulgaria obtained as a result of this review allows us to evaluate the poorly known geographic regions on the basis of their species richness. These evaluations, classified into three groups, are shown in Map 20, page.

Rare Species

Map 21 (page ), showing the distribution of Bulgaria's rare bird species, is based on information about Bulgaria's breeding birds. Two groups of species have been included in this category:

1. Globally threatened species included in the European Red Data List.

The European Red List consists of 29 species, 16 of which are found in Bulgaria and 9 of which breed or occur during the breeding season in the country:

Pelecanus crispus
Halietor pygmeus
Milvus milvus
Haliaeetus albicilla
Aegypius monachus
Aquila heliaca
Falco naumanni
Crex crex
Otis tarda

2. Rare and threatened breeding species included in the Bulgarian Red Data Book.

Information on the distribution of 78 rare breeding species, including the 9 species listed above, was used to create the map. Most of these species are also rare at the regional (Balkan Peninsula) and continental scale. The information comes from the Bulgarian Red Data Book and from unpublished data submitted for the "Atlas of the Breeding Distribution of the European Birds."

The following levels of species rarity are depicted on the map:

0 to 15 species - low rarity
16 - 30 species - medium rarity
> 31 species - high rarity.

The Bourgas region had the highest level of rarity (48 rare species in an area of 2500 km2), followed by the Black Sea coast (between 30 and 40 species), the Srebarna region (40 species), Russenski Lom (39 species), the central Stara Planina Mountains (38 species), the Sofia region (36 species), the eastern Rhodope Mountains (33 species), and Belene (31 species).

Endemism

In the past, eleven bird subspecies were described as unique to Bulgaria but these are now accepted as synonymous with previously published species.

Unique Ecosystems, Habitats, and Communities

In preparing this discussion and the accompanying map (Map 22, page 828), three types of unique communities have been identified: communities unique for Bulgaria; communities unique for Europe; and communities unique for the world.

Two Bulgarian natural sites were included in the International Convention for Protection of the World Cultural and Natural Heritage. These are the Pirin National Park and the Srebarna Natural Reserve. They are both of great importance for the conservation and protection of bird species.

The region of Shabla and Durankulak Lakes is also of global importance. Almost the entire global population of the red-breasted goose (a total of about 60,000 individuals) winters there. The geese spend the period between October and March there, roosting at night in the lakes and feeding in the winter wheat field during the day.

The follow regions are unique at the continental scale:

1. The Bourgas lakes and adjacent lands. This is an important bottleneck area. In Europe other regions of this type include the Bosphor, Gibraltar, and Falsterbo (in Sweden). Almost the entire population of the white stork flies over or overnights in the region of the lakes near the town of Bourgas. The same is true of the white pelican, lesser spotted eagle, and red-footed falcon.

2. Riparian forests. In particular, the forests along the lower stretches of the small rivers of Batova, Kamchia, Ropotamo, and Veleka, with their distinctive bird communities. Unfortunately, some of these areas have been strongly influenced by anthropogenic factors (e.g., the riparian forest "Baltata" on the Batova River).

3. The eastern Rhodope Mountains. This region is high in numbers and density of rare and threatened species (e.g., black vulture, griffin vulture, egyptian vulture, black stork, and white-tailed eagle) and in species richness. It should be noted that the highest numbers of birds of prey in Europe have been found in the southeast part of the Rhodopes in Greece, near to the Bulgarian portion of these mountains.

4. The Island of Vardim. Supports a unique combination of very old flooded forest of Quercus robur, Salix alba, and Populus nigra and large breeding colonies of cormorants, pygmy cormorant, grey herons, purple herons, squacco herons, night herons, little egrets, spoonbills, and glossy ibises.

The Atanassovsko Lake Natural Reserve, which contains the greatest number of rare and threatened bird species, is unique at the national scale.

In conclusion, it should again be pointed out that, although small in territory, Bulgaria is remarkable for its relatively high number of unique bird habitats.

Ecological Services

One of the two most important European migration routes, the Western Black Sea migration route (also known as the Via Pontica), crosses Bulgaria (see Map 23, page 829). This is a result of our country's central location in the Balkan Peninsula and in the Western Palearctic biogeographic region. The species composition and number of migrants, main routes, flying heights, and migration pe-riods and peaks have been described in detail by Michev (1984).

Another migration route - the Via Aristotelis (so-called because of Aristotle provided the first description of it) crosses northeast Bulgaria and the Sofia Plain and continues along the Strouma River valley. There are smaller migration routes along the valleys of the Maritza and Tundzha Rivers. Relatively large migration flights have been observed near the Island of Belene and the Srebarna Reserve.

In the winter, high numbers (about 150,000 - 200,000 total) of white-fronted geese, red-breasted geese, greylag geese, lesser white-fronted geese, mallards, green-winged teals, and pintails congregate in the region of Durankulak and Shabla. There is also a winter concentration of the white-fronted geese (an average of about 30,000 birds) near the Ovtcharitsa reservoir.

During the spring and winter, waterfowl and many birds of prey and passerine birds are concentrated in the region of the Bourgas lakes. It is difficult to ascertain a total number for these birds.

Fragility

We regard as the most fragile and vulnerable the eco-systems along the Danube River and the Black Sea coast, as well as the ecosystems in the valleys of the following rivers: Iskar, Yantra, Russenski Lom, Kamchia, Strouma, Mesta, Tundzha, Maritsa, and Arda. (Fragility and threats are depicted together on Map 24, page 830).

The ecosystems of the high mountains are also highly vulnerable. This is especially true in regions where tourism and winter sports are well developed, including the alpine parts of the Vitosha, Rila, Pirin, and Stara Planina mountains.

The agricultural lands of Dobrudzha should also be included in this category. In the winter of 1988 large amounts of poisons were used unreasonably in an attempt to control rodents. The result was the extermination of thousands of geese, ducks, rabbits, deer, and other wildlife.

Threats

Direct Persecution

Birds are directly persecuted by poachers, photographers, scientists, bird-watchers, forestry workers, tourists, and others. This is a problem throughout the country, especially in the outlying areas of the protected areas. Unfortunately, there are many cases of infringement on these conservation areas.

Recently the number of Bulgarian and foreign hunters in the region of Shabla and Durankulak has increased. In January 1993 we found a dozen hunter-killed red-breasted geese. We further ascertained illegal shooting of wintering geese in the places where they roost at night. The poachers enter these places at night by boat. This practice is especially harmful.

Many songbirds are caught for home-breeding during their migrations and while wintering in the Bourgas lakes region.

Indirect Persecution

Indirect persecution takes a number of forms.

1. Habitat destruction. This includes a number of activities: draining of marshes and swamps, felling of natural forests on the Danube islands and their replacement with hybrid Populus, felling of old forests and their replacement with Pinus plantations, destruction of dunes along the Black Sea coast, and so forth.

2. Shortage of food. This is characteristic of the region of the Danube, where fish supplies have decreased.

3. Over-use of pesticides, fertilizers, and other chemicals. This causes the eutrophication of many wetlands (e.g., Srebarna, Shabla, Durankulak) that are important bird habitats.

4. Over-exploitation. This category includes the destruction of the predominant part of the Quercus forests of Strandzha Mountain, the Fagus forests of the Stara Planina Mountains, and the coniferous forests of the Rhodope, Rila, and Pirin Mountains. The over-exploitation of water resources of the Shabla and Durankulak Lakes leads to changes in their water regime, followed by abnormal decreases in water surface and eventually changes in the fish fauna. This activity presents a danger to the large breeding colonies on Vardim Island.

5. Collisions
a) With cars. Data about the actual numbers of birds killed in such accidents are inadequate.
b) With airplanes. Dozens of accidents are reported for the airports at Bourgas, Varna, and Sofia.
c) With powerlines. This occurs most frequently during the autumn migration in southern Dobrudzha and in the region of Bourgas. White storks are often the victims of these collisions. On occasion, more than ten birds have been found dead as a result of collision with high voltage powerlines. The powerline in the region of the Atanassovsko Lake Reserve is situated crosswise to the direction of the migration.

6. Petroleum and oil pollution. This has become a more frequent phenomenon in recent years and is of special concern in the regions of Tjulenovo, Dobrich, and Bourgas, where white pelicans, swans, ducks, and other waterfowl covered by petrol are very often found.

Sites Containing the Most Representative Samples of Bulgaria's Biodiversity

Habitat types are represented by different patterns in Map 25, page 831.

1. Salt marshes

2. Coastal sand dunes and sand beaches

3. Sea cliffs

4. Islets

5. Lakes, marshes, reservoirs, and rivers

6. Steppes and pseudosteppes

7. Wet grasslands

8. High mountain grasslands

9. Pseudomaquisses

10. Community of Paliurus aculeatus

11. Deciduous, coniferous, and mixed woodlands

12. Riverside and flooded forests

a) Along the Danube River

b) Along the Black Sea Coast

c) Inland

13. Rocky habitats

14. Agricultural ecosystems

15. Urban areas

Species of Proven or Potential Economic Importance

1. White-fronted goose. The White-fronted goose causes damage to agricultural crops in the region of the Shabla and Durankulak Lakes, near the Ovtcharitsa reservoir, and in the region of Bourgas. The damage caused by the birds is sometimes quite significant. This damage could be estimated on the basis of insurance payments.

2. Cormorant. Cormorants cause damage to fish farms in Orsodzha, Karaissen, Mechka, Nova Cherna, Tchelopechene, Blagoevgrad, Samokov, Bourgas, and other areas. Numerical data are not available.

3. Starling. Starlings cause damage to vineyards and fruit gardens throughout the country, particularly when they form large (up to 10,000 individuals) flocks. Numerical data are not available.

4. White stork. During migration this species causes frequent electricity cut-offs in South Dobrudzha and in the Bourgas region. Several other waterfowl species have caused air-crashes. Numerical data are not available.

Historic, Current, and Potential Threats

Negative impacts on the Bulgarian avifauna were first identified in the earliest years following the liberation from the Turkish regime. These impacts involved mainly indirect damage to several species as a result of the uncontrolled cutting of forests and land reclamation.

The small arms and other weapons kept by people after the wars at the end of the last century, and especially during the beginning of this century, resulted in uncontrolled and unregulated hunting. Many birds - especially of the larger and more curious species - were killed off. Mass killing focused on the birds of prey and birds used as food.

There are numerous customs and traditions connected with the killing of birds in many towns and villages of the country. For example, many ice-covered great bustards have been caught during hard winter periods in Dobrudzha. Birds of prey have been caught by traps for their fat, which is used for medical purposes. Body parts of many birds (especially eagles) have traditionally been used in occult preparations. These activities, coupled with the lack of legislation for nature protection, damaged some species considerably.

Vulture populations were harmed by the mass use of strychnine baits against wolves. This practice began at the end of the last century and continued up to the 1960s. In the years since, and even at the present time, strychnine has been used on occasion for the same purposes.

One of the most significant, far-reaching, and even catastrophic threats to the Bulgarian avifauna has been the mass draining of marshes, swamps, and other wetlands and their transformation into agricultural lands. These activities began in the 1920s with the draining of 100 km2 of the Straldzha Marsh and continued to their apogee during the 1950s. As a result, almost all the marshes along the Danube River, as well as the inland marshes (Dragomansko, Dzhavolsko Blato) and the swamps in the mountains (Batashko Blato), have been destroyed. The breeding populations of many species were severely and fatally affected. These species are now included in the list of extinct, threatened, and vulnerable species.

The beds of many rivers in the Bulgarian lowlands (the Iskar, Vit, Yantra, Ossam, etc.) have been "corrected" and embanked. In the process, many wetlands of value as breeding and feeding sites were destroyed.

An all-out war against birds of prey was carried out beginning in the 1930s. This war became horrific during the 1950s. All possible means - including direct hunting, the destruction of nests, the taking of eggs and nestlings, and the use of poisoned baits - were employed. Despite recent successes in efforts to protect these birds - in 1986 they all became protected by special law - there are currently some dangerous moves afoot to legalize falconries and to remove the conservation status of several birds of prey. This latter move will have a harmful effect on the whole group due to the insufficient biological knowledge of hunters and the fact that most of them cannot or do not distinguish the different species.

Similarly, the fight against fish-eating birds has historically been quite strong, especially during the 1950s. It continues up to the present day with mass fowling in and near fish farms. This trend is likely to be reinforced in the future due to the privatization of the fish farms.

It is highly probable that pesticide use has had serious after-effects on the populations of many bird species. Until the reforms of 1989, the data on this matter were kept secret. We do not have direct data about this threat, except for the finding of DDT in the eggs of the Dalmatian pelican (Michev and Dilchev, 1987). It is not definitely established, however, that Bulgaria was the source of this substance.

Many birds were also killed during the campaign against rodents.

One of the significant threats to Bulgaria's bird life was the mass merger of agricultural fields, especially during the 1950s, when collectivization was carried out.

The building of the Zhelezni Vrata reservoir caused drastic changes in the total discharge of the Danube, and had aftereffects on the Belene, Vardim, Srebarna, and other wetlands alongside the river.

The mass cutting of the forests and their replacement by plantations of exotic tree species has resulted in the establishment of many green spots unsuitable for birds.

Potential threats to the Bulgarian avifauna include the restoration of private control of lands, forests, fish farms, and grazing grounds, and the lack of control over pollution from newly created or privatized industrial sites.

Conservation Recommendations

The recommendations offered here fall into three groups: legal recommendations, management recommendations, and scientific recommendations.

Legal Recommendations

1. Changes in national conservation legislation are needed due to current changes in Bulgarian agriculture and industry.

2. Legislation should be carried out in accordance with the conservation requirements of the European Community.

3. The Ministry of the Environment should be given legal responsibility as manager of all protected areas and species of national and international importance.

4. Meaningful compensation for damage caused by birds needs to be furnished; only token payments are provided at this point.

Management Recommendations

1. A Nature Conservation Agency needs to be established to enforce legislation on biodiversity conservation.

2. The proportion of participation by governmental institutions and non-governmental organizations in the protection of biodiversity needs to be reversed. At present, most conservation activities are assigned to the governmental institutions.

Scientific Recommendations

1. Support is needed for monitoring of the numbers and distribution of Bulgarian birds, the state of their habitats, and the relative degree of influence of the different types of threats.

None of the recommendations proposed in this section will be effective if special measures are not taken to increase public awareness of conservation through education.

Acknowledgements

The authors wish to thank Dr. B. Ivanov and Dr. B. Milchev for their invaluable help in collecting the information included in this report, an Dr. M. Stoyneva for her technical assistance and helpful comments on the manuscript.

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