State of the white stork Ciconia ciconia population in the peripheryof breeding range and expansion to the east

摘要

White Stork Ciconia ciconia expands its breeding range in Europe to the east during last centuries. This process has wave-like pattern: periods of expansion alternate with recoils. The breeding range pulsates and are gradually enlarged. In Ukraine in the second half of XX super(e) century such pulsation went in east regions. There is an interesting contradiction: storks continued advance to the east and its number in these regions increased in spite of total number decreasing of the species and depression of populations in many countries. In other parts of Ukraine population of the White Stork was also in depression at this time. Monitoring of the White Stork population in Ukraine in 1992-2004 allows to explain this phenomenon. We studied breeding success and number dynamics of the species on the net of control plots. It turned out, that breeding success in peripheral part of the range is significantly higher, than in main parts. In west Ukraine the average number of fledged youngs per successful pair makes up (M plus or minus sd) 2.64 plus or minus 0.37, per breeding pair - 2.48 plus or minus 0.21 (n = 175); in south Ukraine: 2.87 plus or minus 0.59 and 2.69 plus or minus 0.64 (n = 30); in north-east Ukraine: 3.21 plus or minus 0.58 and 2.80 plus or minus 0.71 (n = 91); in the Middle Dnieper area: 3.11 plus or minus 0.69 and 2.67 plus or minus 0.65 (n = 129). The highest parameters have Poltava (3.56 plus or minus 0.45 and 3.18 plus or minus 0.58, n = 38) and Kharkiv (3.36 plus or minus 0.51 and 3.06 plus or minus 0.70, n = 10) regions. These figures are also bigger, than in central and west Europe. Higher breeding success in peripheral parts of stork's range was found also in Russia. Therefore, in this case the periphery of distribution area is all-sufficient for the further expansion.