Are these four all male Red-breasted Mergansers in eclipse ? ( ignoring the wigeon )
No interactions present.
Note the diffuse border betweent the rufous head and the grey neck, Goosander is more sharply defined.
thanks for your helpful comment.
Lat/Lng: 53.2967, -4.2055
OS grid ref: SH531800
shallow, tidal sand/mudflats