Phenological changes in the wintering end date of Pelophylax ridibundus (Pallas, 1771) (Ranidae, Anura) in the Medveditsa river valley (Saratov region) under conditions of climate transformation

The time series of dates of the end of wintering and the beginning of spawning migrations of the marsh frog in the valley of the middle reaches of the Medveditsa river (Don basin, Saratov region) was analyzed. It has been established that in the period from 1892 to 2021, the phenological norm of this phase of the annual cycle shifted to earlier dates by an average of 6 days (from May 2 to April 26) against the background of climate warming. Possible consequences of this transformation of the spring phenology of anurans in connection with the changes established are discussed. Continued monitoring of phenological changes in the spring phase of the annual cycle is required to form a forecast of the population dynamics of this anuran species and the scientific basis for their conservation.