Relationships among wing length, wing shape and migration in Blackcap Sylvia atricapilla populations

Wing length was measured and wing formula recorded for 182 male Blackcaps. These two characters were closely related; frequencies of the three different wing formulae vary in relation to wing length, so that the pointed wing is mostly recorded for longer wings, while the rounded one has a higher frequency among birds with shorter wings. It is suggested that wing formula and wing length are closely related to the migratory tendency of each Blackcap population. Southern populations have a shorter wing, and a rounded one; ringing data show them to be resident or only partially migrant. We suggest that the altitude of breeding areas has the same effect on the population morphology as latitude. In two Sicilian populations of Blackcaps, that breeding at 1700 m has a longer and more pointed wing than that breeding around sea level.