What is cited as the absolute best field mark for positive identification of a Redwing (*Turdus iliacus*)?

The striking cream or pale yellow supercilium contrasting with the dark eye-stripe

The key to positive identification of the Redwing, even at a distance or during flight, is its facial pattern. Specifically, the presence of a striking supercilium—the stripe located above the eye—which is described as being cream or pale yellow. This feature stands out sharply because it contrasts directly with the dark stripe located beneath the eye. While other features like the reddish flanks or the reddish-orange underwing flash in flight are also important markers, the strong contrast and definition of this pale stripe above the eye are highlighted as the single most reliable characteristic for differentiating it from close relatives like the Song Thrush or Mistle Thrush.