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 Stork’s 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 1992–2006.
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: vgrishchenko@mail.ru.
