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1 2005

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Does egg sex ratio in Urban Kkestrels (Falco tinnunculus) differ from parity?

Rejt Ł., Gryczyńska-Siemiątkowska A., Rutkowski R., Malewska A.

Polish Journal of Ecology

2005

Vol. 53, nr 4

545-552

Paper tests the hypothesis that urban kestrels (Falco tinnunculus) are sex biased connected with urbanization gradient (central zone vs suburbs), laying date and level of PCB-contamination. Blood samples of 158 nestlings were collected on FTA cards. Sex of nestlings was determined using a multiplex PCR technique. Egg sex ratio among kestrels in Warsaw (Poland) was 51% and did not differ significantly from parity (n = 34 nests). Among broods at the beginning and at the end of the breeding season proportion of males was significantly higher than in the middle of the season. Sex ratio was significantly different along the urbanization gradient. Proportion of males in broods at the central zone reached only 44% contrary to the external zone where males composed 65% of chicks. Possibly influence of laying date, female condition as well as population size and isolation is discussed. For assessing the level of PCBs small amount of blood (approximately 1 mm3) was collected from the brachial vein from 83 individuals (17 nests). All samples from a particular nest were pooled together to increase the possibility of successful analysis. Among most broods (pooled data for nests with complete and partial hatching) contamination of PCBs in nestlings. blood was low (average level of PCBs was 55.1 ppm, range: 0-252.8). A trend toward decreasing proportion of males among broods with higher PCB-contamination was found to be insignificant. Probably level of organic contamination in chicks. blood depends more on pollution existing in rural hunting areas and is not directly connected with nest site and its close vicinity.