Małgorzata Ginter1 and Michał Kaszuba2
1Bird Migration Research Station, University of Gdańsk, Przebendowo, 84-210
Choczewo, Poland
2Department of Molecular Cytogenetics, Institute of Genetics and Animal
Breeding Polish Academy of Sciences, Jastrzębiec, ul. Postępu 1, 05-552 Wolka
Kosowska, Poland
biomgi@univ.gda.pl
Robins migrating through the Polish Baltic coast were sexed by gonadal
inspection (119 dead birds found in years 2001-2006) and molecular techniques
(189 feather samples from birds caught in 2006). Linear measurements were
taken (wing length, tail length, wing formula, bill length, total head length,
tarsus length) and amount of greyness on head and side was determined.
Feathers from some dead birds were also used to genetic analysis and
repeatability of sexing by these two method was checked. The aim of this study
was to propose measurements which could be helpful in sex determination of
migrating Robins.
Percentage distribution of different measurements in both sex groups
was presented and averages of all measurements between sexes were
compared by t-test or Mann-Whitney U-test respectively. Next conceptual
models to explore possibility of sex determination based on combination of
different measurements were presented by GLM method. Analysis was done for
both age groups jointly as well as only for immatures and for birds sexed by
both methods as well as for each method separately.
The results showed that wing, tail and total head length differred
significantly between sex groups (p<0.001). Among these three measurements
only wing length and total head length were a decisive criterion in sexing
immature birds. Ranking of models in GLM method showed that also tarsus
length improved sex determination of Robins. Tarsus length and total head
length index is recommended as a better indicator of body shape than total head
length itself and it could be more useful in sex determination.
In Fennoscandian Robins differences between sexes refer to wing length and
tarsus length. In Robins migrating through the Polish Baltic coast tarsus length
undirectly differ between sex groups. The results showed that females were
smaller than males but they had longer tarsus. Combination of body size and
body shape parameters could improve sex determination of Robins.




