Piotr Profus

SEX-RELATED NATAL DISPERSAL OF WHITE STORKS (CICONIA CICONIA) IN POLAND: HOW FAR AND WHERE TO?

Abstract Distance and direction of natal dispersal were studied in a Polish White Stork (Ciconia ciconia) population on the basis of 25 years of banding and resighting data. Multiple regression analysis showed a significant sex-linked bias (females settled farther from the natal sites than males) and effect of banding year, in that dispersal distances were decreasing toward the end of the study period. Population indices in the hatching year and the presumed recruitment year did not help to explain the variance. The birds showed a trend toward settling southeast of the natal site, but this was significant only in individuals that settled within 50 km of the natal site. We suggest that when returning from winter sites in the southeast, young White Storks settle before they reach their presumed migratory target in the vicinity of the natal site. This is only possible if, in spite of a relatively high population density, many breeding areas and potential nesting sites remain vacant. This might also explain our failure to find density dependence in the interannual variation of dispersal distances.

Potential impact of wolves Canis lupus on prey populations in eastern Poland

Abstract A 7000 km2 study area in eastern Poland supported c.50 wolves Canis lupus in 1989 and 40 in 1992, and high numbers of game constituting the staple food of these predators. This paper assesses the energetic requirements of the wolf population as well as potential resources of its preferred prey. On the basis of basal metabolism rate (BMR) and daily food consumption (DFC), we calculate that an average wolf (35 kg) needs 13 421 kJ daily, which corresponds to 1·74 kg of prey biomass. Calculations based on field metabolism rate (FMR2-for non-herbivorous mammals) yielded a 60% higher value, i.e. 2·77 kg of meat per day. The yearly requirements of the study population, using these two methods, ranged from 242 GJ (40 individuals, BMR and DFC) to 389 GJ (50 individuals, FMR2), i.e. 31·5–51·0 tonnes of meat and edible tissues. Wolves preyed chiefly on red deer Cervus elaphus and roe deer Capreolus capreolus (70–85% of the total biomass consumed), wild boar Sus scrofa, hare Lepus europaeus, moose Alces alces and small rodents. The total biomass of wolf prey, censused from snow tracking and year-long observations, and corrected from drive censuses, was assessed at 879–943 tonnes. These data suggest that wolves remove no more than 10% (6·3–9·0%) of the total available biomass of ungulates which may not seriously affect resources of local game owners.

The relationship between population means and variances of reproductive success differs between local populations of white stork (Ciconia ciconia)

We studied the size and productivity of white stork (Ciconia ciconia) populations in eight study sites in Poland. The number of nesting pairs and the average number of chicks fledged per pair fluctuated over time, and the studied populations differed in the variance of both breeding success and number of breeding pairs. The variance of breeding success (both for the mean number of chicks and the proportion of successful nests) and the variance of the number of breeding pairs was not correlated with the extent of stable habitats (pastures, meadows, wetlands), other habitats (farmland), or with local population trends over time. We found a non-linear symmetrical relationship between annual mean reproductive success and its variance but only when considered as the proportion of successful nests (i.e., when individual nests are coded as a binary value: 0, no success; 1, success). No such relationship existed when success was expressed as the number of fledged chicks. Although a positive significant correlation occurred between fledgling numbers (discrete data) and the proportion of successful nests (binary data), we believe that the use of only binary data will be inadequate in more detailed analyses, such as population viability analysis.