Een kraaien- en kauwenslaaptrektelling ‘uit de oude doos’

this note analyses the course of roostmigration/flight of ‘crows’ (identified and unidentified Carrion and Hooded Crows and Rooks) and Jackdaws to a woodland area between The Hague and Leiden during a winter afternoon in 1974. Severat aspects of ‘crow’ migration (arriving in the roosting-area, leaving it again, building up the roosting population) are shown to develop gradually over time, while Jackdaw migration is developing rather jumpy at the same time. These findings reflect that crow roosting migration is very much a solitary individual activity, while Jackdaw migration is a social group activity, in which the members of the group constantly and clamorously are synchronising their activity (coming, staying or leaving).