Correlation between phenology of migrations and breeding success of the
White Stork in Ukraine. - V.N. Grishchenko. - Berkut. 15 (1-2). 2006. - P. 85-93.
Migratory birds which arrive earlier on their breeding grounds have as a rule higher reproductive success. This phenomenon is well studied for the White Stork. We tried to analyse the correlation between timing of arrival and departure and breeding success at the population level. Border of White Storks breeding range passes in Ukraine through eastern regions and the Crimea. Ukrainian population of the stork can be divided in two parts which have qualitative differences: core and peripheral ones. Their limits pass approximately along the Dnieper area. Data on the breeding success were collected during monitoring of the White Stork population on a net of study plots (195 plots in 23 regions) in 19922006. For the analysis of phenology medians were calculated using different sources (1281 dates for the first arrival and 443 dates for the last departure). Calculations were conducted for the whole territory of Ukraine and two above mentioned parts of the stork population. Two years during the period of study were exceptional: 1997 and 2005. These were so-called catastrophic years with drastic decreasing of number and breeding success of the whole population. These features were also considered. Correlation between reproductive parameters and timing of arrival reveals itself only for the whole period in 15 years and disappears at exception of two catastrophic years (Table). Therefore, in normal years the reproductive success is independent from arrival timing of population. In catastrophic years all the analysed parameters considerably deviate from usual values. This is a consequence of bad conditions on wintering grounds: birds return weakened with a delay in time and raise less youngs. Many pairs breed unsuccessful. The core and peripheral parts of the White Stork population show different features: in peripheral part the influence of catastrophic years is less, but there is a positive correlation between mean number of youngs and time of arrival in normal years. Dates of departure do not correlate neither with breeding success nor with arrival. These results are preliminary, because the analysis was conducted for a short time period. Nevertheless, the described tendencies are interesting and need more detailed study. At least, they confirm qualitative difference of two parts of the White Stork population. [Russian].
Key words: White Stork, Ciconia ciconia, Ukraine, migration, breeding success, phenology, population.
Address: V.N. Grishchenko, Kaniv Nature Reserve, 19000 Kaniv, Ukraine; e-mail: email@example.com.