Scandinavian Rock Pipits in our estuaries?

At the same place where I photographed the Meadow Pipits over a week ago was this Rock Pipit on the 9th. When compared with the Meadow Pipit, Rock Pipit is slightly larger and darker with more diffuse steaking. This is especially so on the flanks where the streaks merge into a dusky smudge on the rear flanks. I suspect most birds that appear in our estuaries in winter are of the Scandinavian race littoralis as there is definitely a greyer and paler appearance in comparison with the more olivey local birds occupying the rocky coast. These birds can sometimes have surprisingly strong supercilia and pale underparts and in bright light can resemble Water Pipits, but this species is always a warmer brown tone with whiter underparts and more clear-cut streaking, without the dusky rear-flank.

The suspiscion that some birds are littoralis is often confirmed in spring when birds moult into their breeding colours and small migratory flocks form before departure. However, in winter plumage, differences are probably not distinctive enough to confidently claim these greyer birds are categorically of Scandinavian origin. Perhaps some ringing may be on the cards?