Long-term trends in phenological dates of bird arrival in Petrozavodsk City surroundings are analysed for 12 species ofshort-distance migrants over a 35-year period (1971-2006). Simultaneously, correlations between spring arrival dates and fluctuations of population abundance (density) in individual species are considered. At present, Rook, Starling, Lapwing and Skylark arrive 1-2 weeks later than in the 1970s-1980s, when winter was milder, and spring was warmer and came earlier. The shift towards later dates of arrival in these species is due to the ongoing phase of abundance depression in Starling, Rook, and partly Lapwing, observed in peripheral northern populations.
Spring arrival of Common, Herring and Lesser Black-headed Gulls in the past decade is 2-3 weeks earlier than in the 1970s and early 1980s. The reason for that is a rise in the abundance of the species in cities, and the fact that they now feed mainly in urban areas - landfills, garbage containers, waterfowl feeding areas, etc. Furthermore, phenological dates of arrival in Common and Black-headed Gulls, which are numerous in Petrozavodsk surroundings, correlate with periods of rise or decline in the abundance of suburban breeding colonies. Non-periodic changes in spring arrival dates are demonstrated by Little Gull; 3-6-day earlier arrival dates (1980s, 2001-2006) coincide with phases of abundance rise in suburban colonies, and with the principal stages of the species overall expansion in Northwest Russia. In 1991-2006, Bean, White-fronted, and Barnacle Geese started spring passage 1-2 weeks earlier, and concentrated in great numbers in stopovers in farmland in southern Karelia. Presumably, the reason is growing continentality of the climate, and displacement of goose spring migration routes from regions in the centre of European Russia to westerner regions (Karelia, Leningrad Region, and western Arkhangelsk Region), closer to the impact zone of peri-Atlantic climate conditions.
Thus, long-term dynamics of phonological dates of bird arrival depends, in addition to global climate changes (e.g., warming events of the 1880s, 1930s and 1970-1980s), on secular fluctuations of range boundaries and abundance of individual species. Long-term and steady arrival earlier than many-year averages indicates onset of the species expansion or abundance rise, whereas a lag in arrival dates is evidence of expansion fade-away or onset of the abundance decline phase.