SEEN - SE European Bird Migration Network
Sex-age composition of migrating Blue Tits (Parus caeruleus)
Jacek Chruściel
Bird Migration Research Station, University of Gdańsk, Poland

This work presents analysis of Blue Tits sex–age composition during migration at two ringing stations located on the southern Baltic coast – Mierzeja Wiślana and Bukowo-Kopań. In total nearly 50 000 individuals were caught in years 1967 – 2004. Data collection was done according to standard Operation Baltic methods that included continuous mist-netting during whole migration season. Details of the methods are given in “Bird Station Manual” (Busse 2000). It was found that sex–age composition at both Polish stations did not differ. Immature birds composed 90% of caught birds. In both age groups (adultus/ immatures) more females, 60%, than males were observed. There was no correlation between age–sex composition and migration intensity (stat. insignif.). Sex–age composition general pattern was similar to that observed at other bird ringing stations in the area. However sex–age composition at Falsterbo ringing station was different. There was more young females in Falsterbo than at Polish stations.
Generally, migrants’ sex–age composition is a result of differentiated migration disposition of individuals of different sex and age groups as well as different individual status in population. Still, details of the phenomenon should be studied.
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