Wyniki liczenia gniazd bociana białego (Ciconia ciconia) na terenie byłych powiatów Bełchatów i Sieradz

In 1984 the nests of the White Stork in the area of the former Bełchatów District (734 km2) and a part of the former Sieradz District (about 720 km2) were investigated. Comparisons were based on questionnaire data from 1968-1970 and on an inspection from 1974. 42 (5.72 nests /100 km2) and 35 (4.86 nests/km 2) nests, respectively, occupied by pairs were recorded. In the whole course of the investigated period the percentage of nests with no breeding success (HPo) increased exponentially. Changes in the efficiency of breeding from year to year resulted mainly in changes in the differences in the percentages of nests having extreme numbers of young birds which had left the nests. A negative influence of the mine upon the efficiency of breeding of stork nesting within an area adjoining a strip brown coal mine was proved.