Horned Grebe, Lake Myvatn
Also known as Slavonian Grebe, we see these on the east coast of US in winter. They are also seen on Irish coasts and bays in winter. (I have seen them over the years in Wexford Harbour, rare but mixed in with Great Crested Grebes.) In winter they lose the spectacular breeding plumage and are instead various shades of grey and white.
Canon EOS-1D X, f/9 @ 400 mm, 1/640, ISO 200, No Flash
T.Michael Redmond