Mute swan (Cygnus olor Gmelin 1789) in the eastern part of the Gulf of Finland: history of dispersion, distribution of breeding birds and features of biology

Abstract

The description of the main events of a Mute swan reproduction in the eastern part of Gulf of Finland is given: terms of arrival, spatial and biotopical distribution on nesting, terms and success of reproduction, features of bird behavior. A comparison with data from other parts of an area is carried out. Success of nesting in open biotopes of sea islands is caused by behavioural plasticity of Mute swan. Features of ecology of local birds are most similar to those of swans from Estonia, Finland, Sweden and Denmark. Large delay of dates of reproduction start and marked reduction of average size of laying from southern populations to northern populations are noted in the eastern part of Baltic region that speaks about an inaccuracy of the conclusions of a some authors about uniformity of reproductive indicators of Mute swan of the Caspian and Baltic populations. Refs 76. Figs 13. Tables 10.