Underwing colour (and particularly the colour of the underwing coverts) is a very useful guide to quick identification of fly-through thrushes. Fieldfares and Mistle Thrushes have clean white underwing coverts. Song Thrushes have yellow ochre underwing coverts, and Redwings have red ochre underwing coverts. Some of the rarest thrushes, including the tiny Catharus thrushes from North America and the Asiatic Zoothera thrushes, have banded black and white underwings.
Song Thrushes uniquely smash snails on stones Redwing: red/ orange underwing Blackbirds eat proportionately more fruit than Song Thrushes Fieldfare: white underwing Song Thrush: yellow ochre underwing