Ardea
Official journal of the Netherlands Ornithologists' Union

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Wysocki D. (2004) Within-season divorce rate in an urban population of European Blackbird Turdus merula. ARDEA 92 (2): 219-227
The within-season divorce rate of the European Blackbird Turdus merula was studied in 1997-2003 in two city parks in Szczecin (NW Poland). Within the population studied, 14 and 11% of pairs in each of the park were observed to divorce, the early-mated pairs divorcing more seldom (11 and 10%) than the late-mated pairs (48 and 15%). Significant differences in the within-season divorce rate was found between successfully and unsuccessfully breeding pairs in Park Z. Females that switched males did not pair up with larger males. Individuals initiating the divorce did increase their breeding success, as opposed to the deserted partners. The causes underlying within-season divorces may be divided into the following two groups: usurpation (22%) and. escape from the territory (78%). The frequency of various divorce causes was found to be plot quality dependent. Usurpation caused 39% of divorces in plots having the highest fledgling production, while in areas with poor success only 11% of the divorces had this cause and escape from the territory was predominant. No statistically significant relationships between the within-season divorce rate and the number of single males and the number of broods in a given year was found.


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