Do numbers of Great Tits Parus major caught at ringing stations reflect the real intensity of passage?

Abstract

The capture dynamics for Great Tits Parus major ringed in the years 1979—1993 at six stations on the south-eastern Baltic coast between Estonia and Poland formed the basis of an analysis as to whether the captures at one station were sufficient to describe the large-scale migratory activity of birds in the region. The centrally located Neringa station served as the focal station and the five other stations as points of reference. It emerged that both seasonal and multi-year capture dynamics for Neringa were usually well correlated with results from the remaining five stations. However, the highest correlation (for multi-year dynamics r = 0.78; for seasonal dynamics r = 0.77) was found when the results from Neringa were compared with the intensity of Great Tit migration in the whole region (calculated as the mean for the remaining stations). The results show that, in the case of a migrant with a simple migratory system, such as that of the Great Tit, the number of birds caught at one specific ringing stations often is sufficient to map the migration intensity of a larger region, but also that many stations give a still better measure of the passage intensity. Equally, the Great Tit’s migration over large areas is shown to be surprisingly even.