Ooooo I actually know the answer to this one.
Dawn Sarf we mostly have resident blackbirds. They’ve lived here a long time and they like their patch. They live on their own and like to keep it that way, unless it’s spring time and they want to get horny.
Come Winter, well that’s when all the scandis arrive. This bunch of hooligans have eaten all the berries in Scandinavia and flock together to migrate southward, many arriving in Scotland. They’re still blackbirds, but you’ll see very different behaviour for such a flock in Scotland than a resident individual in southern England.