Redwing having a field day in bad weather
There are good reasons for this being closely related members of the thrush family. Both are winter visitors to Ireland that arrive and depart at around the same time. They often travel around the countryside in mixed flocks.
But they never mix during the breeding season because they come to us from different parts of the world. Almost all the redwings that over-winter in Ireland belong to a sub-species that spends the summer in Iceland and the Faroe Islands and which have recently colonised part of south Greenland. Fieldfares have a huge breeding range across northern Europe and north Asia but almost all our birds come to us from northern Norway and Sweden or Finland.