Abnormally Early Nesting of Acanthis cannabina (Linnaeus, 1758) (Fringillidae, Aves) in the Latryk River Valley (Saratov Region)

During our field research in March–May of 2017–2020 in the valley of the Latryk river (Saratov region), it was found that the phenological norm of the beginning of the nesting period of Acanthis cannabina should be dated as the last decade of April. However, under conditions of the local climate transformation, its stability is lost and the emergence of an abnormally early start of the reproductive period of A. cannabina becomes possible. The oviposition onset of A. cannabina could be stimulated by two meteorological factors, namely, a rapid increase in the average daily temperature and, to a greater extent, an increased intensity of ultraviolet radiation in the spring.