What is a key identification marker for a Horned Grebe in its non-breeding plumage?

Answer

The clean, sharp delineation between the dark cap and the white neck/face

While the breeding bird is identified by ear tufts, the winter bird is best marked by the clean contrast where the dark coloration of the cap meets the pale face and underside.

What is a key identification marker for a Horned Grebe in its non-breeding plumage?
raritybirdwaterfowlGrebe