Dynamics of the Number of Anatids (Anseriformes, Anatidae, Aves) in Model Regions in Dagestan

The decrease in the number of waterfowl and near-water birds on a global scale is largely associated with a reduction in the area of wetlands in the era of climate warming. On the example of transboundary populations of Anseriformes (Anatidae), data on long-term monitoring obtained in the period 1995–2020 in two Key Ornithological Territories of Russia of international importance (in Sulakskaya and Turalinskaya lagoons, Republic of Dagestan) are reflected. The model lagoons are located on one of the largest Western Caspian flyways in Russia, which is arranged as a “bottleneck,” where the flight routes of European and Asian migrants intersect. A model group Anseriformes, which includes 18 mainly background species, was selected based on the regularity of their encounters during migratory flight. Based on data on ring returns obtained from the Research Information Center for Bird Ringing of the Institute of Ecology and Evolution, Russian Academy of Sciences, a conditional contour of the generalized range of Anseriformes was determined; their faunogenetic basis consists of widespread Arctic and Siberian representatives of the fauna types. According to ringing data and published sources, the geographical location of the anatid populations (regularly migrating through the study region) was determined. It was established that out of 18 species tested, the numbers of 12 species decreased significantly, those of two species increased, and those of four species remained stable. The obtained population trends were synchronized with data from literary sources for the same Anseriformes species, but in their nesting places. The coincidence of the trends indicated above with the population trends of the same species in their nesting places confirms the correctness of the estimation of the number of geographically distant populations of Anseriformes obtained along the their flight routes in the model lagoons. A correlation between the average monthly air temperatures in the autumn–winter period in the Primorskaya Lowland of Dagestan and fluctuations in the number of 12 model species was detected. It was proven that the number of migrating populations of anatids in cold years and the intensity of their flight in the study region increase, while in warm years there was a decrease as a result of delays of migrants on the flight routes and changes in their wintering places. Correlation analysis demonstrated a significant association between the increase in the number of Anseriformes wintering in the Caspian Sea and sea level regression, in which the shallow region of marine waters improved the access of anatids to food resources (benthos). Three key factors determining the dynamics of the number of Anseriformes populations are discussed: hydroclimatic cycles, anthropogenic effect, and foraging. It is recommended to introduce a temporary ban on hunting of eight vulnerable species (greylag goose, common teal, garganey, gadwall, Eurasian wigeon, northern pintail, northern shoveler, and common pochard) in Western Siberia, Kazakhstan, the Ural Federal District, Cis-Urals, Volga Region, and the Southern and North Caucasian Federal Districts until their populations are restored sustainably.