POPULATION OF THE SLENDER-BILLED CURLEW BECOMES STEADY, MONITORING RESEARCHES ARE NECESSARY

D.N. Nankinov

Популяция тонкоклювого кроншнепа становится устойчивой, необходимы мониторинговые исследования. - Д.Н. Нанкинов. - Беркут. 7 (1-2). 1998. - Хотя широко распространено мнение об исключительной редкости тонкоклювого кроншнепа, он регулярно посещает Болгарию. В течение последних лет встречи стали более частыми. Также более частые сейчас наб-людения на западном и северном побережье Черного моря и в других местах. Это свидетельствует о начале стабилизации популяции. Благоприятное влияние оказывают уменьшение загрязнения среды обитания, появление неиспользуемых полей и пастбищ, снижение пресса охоты в результате тяжелого экономического кризиса в некоторых из восточноевропейских стран. В последующие десятилетия возможны случайные изменения в успешности размножения тонкоклювого кроншнепа, но в целом численность популяции будет возрастать.
Key words: Slender-billed Curlew, Bulgaria, Black Sea, population, migration, number, stabilisation.

I know that such title will provoke surprise and bewilderment in some naturalists, dilettantes and professional ornithologists, as the word is about one of the rarest and most mysterious bird on the Earth, considered as "undoubtedly dying species" or even as "completely extinct species" (Kozlova, 1962; Ivanov, 1976). There are mentioned lower and lower figures for its number in the literature: 1000 individuals (Sorokin, 1984), 800 (Flint, 1978), 100-400 (Gretton, 1991), 300 (Winokurov, 1982), 50-300 (Baccetti, Zenatello, 1996), 50-270 (Stroud, 1997), 50-200 ("L' Homme et l'oiseau",1995, 1:10), less than 100 individuals ("Dutch Birding", 1988, 10: 145), several dozens of pairs (Kistyakovsky, 1980), etc.

However my observations in Bulgaria and the collected information about the past and the present state of the Slender-billed Curlew (Numenius tenuirostris), make me think in a different way. I have been occupied seriously with its observation in the last two decades. I have recorded it many times. I published several scientific works (Nankinov, 1899, 1991, 1994a, 1994b, 1996, 1997, Nankinov et al., 1998; Nankinov, Minchev in press) and great number of popular articles. I may assert that for the preservation of the Slender-billed Curlew as a species on the Earth, the territory of Bulgaria is very important. My country is situated between the supposed Westsiberian nesting places and the most distant Moroccan wintering areas and so the bird visits it regularly. During the period 1869-1996 there are 88 announcements (495 individuals altogether) about meetings of the Slender-billed Curlew in Bulgaria. From them only for the last six years (1991-1996) these meetings are 48 (or 55 %) and the number of the recorded individuals is 143 (29 %): 1991 - 20 individuals, 1992 - 13, 1993 - 37, 1995 - 2 and 1996 - 71 ones. I must emphasise that only in 1993 a purposeful searching of the Slender-billed Curlew together with a mass inquiry were accomplished. Because of the lack of money during the next years there were no such observations or they were insufficient. However the irregular recordings, strikes the fact that the number of the Slender-billed Curlew in Bulgaria increases, especially in 1996 in comparison with the previous years. If the researches in the last years were of large dimensions and were in different parts of the country then the recorded Slender-billed Curlews would have been several times more. The flock which we observed in spring of 1996 on the Lake Atanasovsko (Nankinov et al., 1998) shows that the migration of the Slender-billed Curlew is in stages and the concentrations on places, favourable for feeding and resting on their route, are of different individuals. For example between 11 and 19.04 the composition of the flock changes as follow: 11, 12 and 13.04 - 3 adults and 1 young bird; 14, 15, 16 and 17.04 - 6 adults and 2 young; 18 and 19.04 - 7 adults and 2 young birds.

In confirmation of our thoughts that the population of the Slender-billed Curlew becomes steady and there are the first steps for the increasing of its number are the more frequent records of the species along the North and West Black Sea coast and on other places: South Ukraine - 2 records in September 1993 (A. Gretton, pers. com.); Southwest Ukraine, river Sarata, 29.09.1996 - 2 individuals (Nankinov, 1997); Black Sea Nature Reserve, 2.08.1995 - 2 individuals and 4.08.1996 - 1+1 birds (Adamatskaya, 1996, 1997); Ukrainian part of the Danube delta, 18.08.1994 - 1 individual; 17.09 and 16.10.1996 - 1+1 individuals on the Romanian part of the Danube delta - "Janosh Kish several times recorded small flocks" (Zhmud, 1997a); 1.10.1993 - 2 birds in Galych district of Ivano-Frankivsk region (Buchko, Shkolny, 1994). We can add the announcement of E. Nowak "about several dozens of wintering Slender-billed Curlews in Iran" (Zhmud, 1997b). I am sure that during the last years on the Balkans and on other places along the migratory route of the species there are others records of Slender-billed Curlews too, which are not published yet and therefore are unknown.

There are two suggestions for the supposed breeding places of the Slender-billed Curlew: the first one - the vast marshes of the Westsiberian taiga and the second one - the forestry marshes, situated amidst of a hilly landscape. It is possible the species to breed on both places, but there can be surprises, and the nesting areas can be several, isolated on great distances from each other. They can be most easily found with satellite following of birds with transmitters fixed on their bodies. It is glad that the Japanese telegraph and telephone corporation and BirdLife International ("Birding World", 1996, 9, 4: 121-122) already work on this problem. In this respect the collaborators of the Bulgarian Ornithological Centre can help as they know best when and where the catchment of the Slender-billed Curlews and the attachment of the transmitters are possible.

I hope that in the next years all nesting places of the Slender-billed Curlews will be found and we will try to estimate its real number. I suppose that its number is not under the critical minimum, the minimum vital population is not reached. Therefore the species increases its number and the chances for its survival are already bigger. Now the stabilisation of the population of the Slender-billed Curlew is stimulated by several factors, but as if three of them are most important. 1. Decreasing pollution (and degradation) of some habitats with harmful for the species substances (poisons, radioactive and industrial wastes, etc.) in the supposed nesting places in Russia and Kazakhstan, as well as along its migratory route, especially in the Eastern European countries: Bulgaria, ex-Yugoslavia, Romania, Ukraine and others. 2. The unkempt agriculture and stock-breeding in the Eastern European countries. Vast areas in regions with previously intensive agriculture and also some pastures, are uncultivated for years. During migrations birds found there security and plenty of fresh food: insects and their larvae, worms, bulbs, green grass. 3. The decreasing activity of the hunters in the same countries and nearly ceased shot of waders in some countries, for example, in the last hunting season in Bulgaria. The mentioned factors are closely connected with the economic crisis, which engrossed during the last tenth years.

The population of the Slender-billed Curlew becomes steady. Its number cased its decreasing. The records of the species become more frequent on the migratory route. In the next decades occasional variations in the breeding success of the birds are possible, but as a whole the population slowly but surely will increase its number. The monitoring researches will prove this. Bulgaria is the country, where such long monitoring researches of the Slender-billed Curlew can be realised by watching its number in different stations. The results of these observations will provide a possibility for an exact registration of the annual variation in the number of the species and also for timely respond against the danger and for the establishing of efficient measures for protection.

Acknowledgement

Many thanks to my students Svetlan Kirilov, Konstantin Popov, Nikolai Minchev, Nikolai Dimitrov, Toni Tonev and Anton Dimov, who helped me in my exploration of the lakes Atanasovsko and Pomoriisko.

REFERENCES

Ardamatskaya T.B. (1996): Record of the Slender-billed Curlew in the Black Sea Nature Reserve, Ukraine, in 1995. - Inf. materials of the Working group on Waders. 9: 34. (in Russ.).
Ardamatskaya T.B. (1997): The Slender-billed Curlew, Numenius tenuirostris, in the Black Sea Nature Reserve in 1996. - Ibid. 10: 39-40. (in Russ.).
Baccetti N., Zenatello M. (1996): Il chiurlottello Numenius tenuirostris: Il plano d'azione per la sua conservazione e le priorita per il futuro. - Proceedings from research to action plans, Bo-logna, Italia 15-17.03.1996. 177-180.
Buchko V.V., Shkolny I.S. (1994): New data on the rare and unnumerous bird species of the Middle Dniester valley. - Berkut. 3 (1): 51-52. (in Ukr.).
Flint V.E. (1978): Birds. - Red Book of USSR. Moscow: Lesnaya promishlennost. 87-149. (in Russ.).
Gretton A. (1991): Conservation of the Slender-billed Curlew. - ICBP Monographs. 6: 1-159. Ivanov A.I. 1976. Catalogue of birds of USSR. Moscow: Nauka. 1-275. (in Russ.).
Kistyakovsky A.B. (1980): Whether the Slender-billed Curlew was kept still? - News in research, biology and distribution of waders. Moscow. 62-63. (in Russ.).
Kozlova E.V. (1962): Fauna of USSR. Birds. Vol. 2. Is. 1. Part 3. Charadriiformes. Subordo Waders. Moscow-Leningrad. 1-433. (in Russ.).
Nankinov D. (1989): The status of waders in Bulgaria. - Waders Study Group Bulletin. 56: 16-25.
Nankinov D. (1991): Sightings of Slender-billed Curlew Numenius tenuirostris (Vieillot, 1817) in the Balkan countries. - Ibid. 62: 24-32.
Nankinov D. (1994a): Bulgaria is of Great Importance for the Conservation of Slender-billed Curlew Numenius tenuirostris. - J. Ornithol. 135 (Sonderheft): 223.
Nankinov D. (1994b): Analysis of the situation of Numenius tenuirostris in Bulgaria. -Preparation d'un Plan de Sauvetage pour Numenius tenuirostris. 2 (17): 1-5.
Nankinov D. (1996): The Contribution of the Bulgarian Ornithological Centre to the Investigation of the Globally Endangered Bird Species. - J. of the Bulg. Acad. of Sciences. 3: 61-65.
Nankinov D. (1997): Record of Slender-billed Curlew, Numenius tenuirostris, in the south-western Ukraine. - Inf. materials of the Working group on Waders. 10: 40-41. (in Russ.).
Nankinov D., Minchev N. (in press): Observation of a Slender-billed Curlew (Numenius tenuirostris) at the Lake of Pomorie (East Bulgaria).
Nankinov D., Kirilov S., Popov K., Dimitrov N., Dimov A. (1998): Beobachtungen an Dьnnschnabel-Brachvцgeln am Atanasov-See in Bulgarien, April-Mai 1996. - Berkut. 7 (1-2): 48-49.
Sorokin A.G. (1984): The Slender-billed Curlew Numenius te-nuirostris. - Red Book of USSR. Moscow: Lesnaya promishlennost. 1: 153. (in Russ.).
Stroud D. (1997): Proposal for international action plan and specialist network for globally threatened waders. - Wader Study Group Bulletin. 82: 34-37. Winokurov A. (1987): Rare birds of the world. Moscow. Agropromizdat. 1-207.
Zhmud M.E. (1997a): Records of Slender-billed Curlew, Numenius tenuirostris, in the Ukrainian part of the Danube delta. - Inf. materials of the Working group on Waders. 10: 41-42. (in Russ.).
Zhmud M.E. (1997b): The Annual Conference of the Wader Study Group in Kasterle, Belgium. 8-11 November 1996. - Ibid. 10: 49-51. (in Russ.).

Dimitar N. Nankinov
Institute of Zoology, BAS
boul. Tzar Osvoboditel 1
1000 Sofia
Bulgaria