Significantly Earlier Spring Migration in Most Bird Species at the Eastern Limit of Europe

SIMPLE SUMMARY: We investigate the first arrival dates in spring of 31 migrant bird species for the period 1989–2022 in the Tatarstan Republic of Russia, towards the eastern limit of Europe. Most (28) of these species significantly advanced their migration during the study period. A number of species traits were investigated to see if these influenced the advances, but no clear relationships were identified, other than that the earliest-arriving species had advanced most. Higher spring temperatures in Tatarstan were associated with earlier arrival, but the possible influences on these birds of the temperatures at wintering grounds and on migration routes remain to be investigated. ABSTRACT: The first arrival dates of 31 species of migrant birds in the Tatarstan Republic of Russia were monitored for the 34-year period from 1989–2022. Trends in first arrival date were evaluated using regression against the year value. Patterns in arrival data with respect to species traits (habitat, migration distance, body weight, etc.) were evaluated using redundancy analysis. Relationships between first arrival dates and Tatarstan temperatures were also evaluated using regression methods of first-arrival date on monthly mean temperatures. Almost all (28 of 31) species revealed a significantly earlier migration arrival date; however, associations between arrival patterns and species traits were equivocal. Warmer temperatures were significantly associated with earlier arrival in 26 of the 31 species, but the relationship was insufficient to explain the average 11-day advance in species. For these species and in this location only the timing and location of arrival are well recorded; the exact wintering areas and migration routes, and the timing of these phases are less well understood. When these become better known, an investigation of the influence of environmental conditions (including temperature) on departure timing and passage timing and speed is recommended.