The breeding population of Magpies in Słupsk increased from 98 pairs in 1979 to 214 pairs in 1991, or by an average of 9.8% per year. An 8.9% fall in the population between 1991 and 1992 was related to neither reduced breeding success nor increased winter losses in the preceding season. Losses of Magpies gathering at winter roosts were between 4.0% (in 1989/90) and 19.5% (1986/87) and the average for 6 consecutive winters was 12.2%. Clutches of 3-8 eggs (mean 5.6) were laid between mid-March and the beginning of June. Young Magpies fledged between early May and late July, with the peak in late May/early June. Successful broods had 1-5 fledglings (mean 2.7). 51 % of 412 studied pairs were successful at their first breeding attempt and 35% of the 203 pairs failing at their first attempt went on to renest. The 38% of these breeding successfully took the overall proportion of successful breeding pairs in the Słupsk population to 57%.
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