Cumulative Effect of Trophic and Weather–Climatic Factors on the Population Dynamics of the Vole-Eating Birds of Prey in Their Breeding Habitats

Resumo

In the period 2001–2016, the authors studied the combined effect of trophic and weather–climatic factors on the population dynamics of three vole-eating bird of prey species on the study area in northern Moscow region, Crane Homland Reserve (56.7573° N, 37.792° E). The numbers of breeding pairs of the Common kestrels (Falco tinnunculus), Long-eared owls (Asio otus) and Short-eared owls (A. flammeus), as well as abudance of small mammals, were counted in the spring and summer months every year. Different indicators characterizing the weather–climatic conditions in the study area over the period of existence of the nesting groups of bird species were calculated based on the data of the nearest meteorological station. The simulation results showed that the numbers of the Long-eared owls depended significantly only on the trophic factor (β = 0.77 ± 0.1). The numbers of breeding pairs of the Short-eared owls and the Common kestrels depended significantly on both factors. The influence of the trophic factor on the change in the numbers of predators was the higher for the Short-eared owl (β ± SE = 1.64 ± 0.16) and the less for the Common kestrel (β = 0.38 ± 0.12). For the Common kestrel, the impact of climatic and weather factors (β = 0.41 ± 0.09) on its numbers slightly exceeded that of the trophic factor. For Short-eared owl, the effect of the climatic factor (β = 0.36 ± 0.09) was 4.5 times less than that of the trophic factor. A combination of temperature and humidity in the spring period can significantly influence the amplitude and frequency of fluctuations in the numbers of the three species of birds of prey under consideration.