Ecology of Anseriformes on lagoons of the western coast of Middle Caspian
Sea. - E.V. Vilkov. - Berkut. 15 (1-2). 2006. - P. 99-119.
Shoals of the Caspian Sea and adjacent water-marsh areas present original habitats for a large amount of Anseriformes. Variations in their number and species diversity are most distinctly seen during the seasonal migrations of birds along the western part of the Caspian Sea: this West Caspian-Nilotic route of Palearctic migrants is considered as one of the largest in Russia. Along this traditional route, migratory birds annually fly for wintering and return from the boreal-arctic, north-east and West Siberian areas of Russia, from Ural, Northern Kazakhstan, the Volga and northwest Caspian regions. Special inclination of migrants to the West Caspian coast is attributed to the southern location of the sea, considerable extension of the coastline (over 1200 km), mild climate and significant number of water-marsh areas (as distinct from the east coast), which draw goose kind for rest, feeding, wintering and nesting. For this reason, migration flow on the west coast of the Cas-pian Sea is 14,9 times as large as on the east one. Historically formed cyclic fluctuations of the sea level cause synchronous redistribution of Anseriformes habitats. Thus after the last transgression which happened at the end of the XX century, an ecologically new complex of saltish lagoons (Fig. 1) free from surface vegetation appeared in the central arid part of the Daghestan coast. Over the years, open water areas of lagoons have turned into freshened reservoirs with the well-developed hydrophilous flora. Optimization of ecological conditions on the ways of the goose kind mass flight has had a positive effect on their number, diversity of species, transformation of migratory behavioural stereotype and duration of stay with the subsequent change in the status of several species (Tables 5, 6). Meridian-directed location of lagoons along the western coast of the Middle Caspian Sea accounts for rather active migration and nomadic existence of Anseriformes which can be observed for 99.5 months of a year (Tables 3, 4). Pronounced specific character of migratory processes is connected with the fact that one of the research zones situated in the mouth of a rather narrow (45 km in width) migration corridor looks like a bottle neck (Fig. 7). Necking of the passageway leads to concentration of the goose kind and mixing of their hydrophilous and conditionally overland migrant types. Totally 31 goose species (Table 1) have been registered in the study area during the nine-year research period of 19952004. On the basis of regular occurrence on the flight route, 18 species of this number (58,1 %) have been determined as model types, the rest as incidental migrants. Relying on observation of long duration, we have managed to make adequate forecasts and to establish trends of number in the model group of birds, having interpreted the whole complex of influencing factors. Our research has shown decrease in number in the majority of model Anseriformes species during the last 9 years (Fig. 6) with the exception of mallards and teals (Garganey, Teal) (Fig. 4); the fact should be regarded as an alarm signal to take urgent steps for conservation of the species both on the regional and global scale. Our findings serve compelling evidence of consequences caused by different transformations in goose number on the most part of their natural habitat, as observations on the main routes of flight allow tracing dynamics in trends of number of the majority of migrant birds, while number fluctuations, in their turn, impartially reflect chronology of depressive processes on a global scale. On this basis, lagoons of Daghestan can be considered as a unique mo-del and a research ground because a long-term study of global natural processes will help to develop a general strategy for goose conservation on the Eurasian scale. [Russian].
Key words: Daghestan, number, migration, wintering, breeding, conservation.
Address: E.V. Vilkov, Caspian Institute of Biological Resources, M. Gajiev-str. 45, 367025 Makhachkala, Russia; e-mail: email@example.com.