171. BROWN-HEADED GULL. _Larus ridibundus_, Linnaeus. French, "Mouette rieuse."[36] This pretty little Gull is a common autumn and winter visitant to all the Islands, remaining on to the spring, but never breeding in any of them, though a few young and non-breeding birds may be seen about at all times of the summer, especially about the harbour. Being a marsh-breeding Gull, and selecting low marshy islands situated for the most part in inland fresh-water lakes and large pieces of water, it is not to be wondered at that it does not breed in the Channel Islands, where there are no places either suited to its requirements or where it could find a sufficient supply of its customary food during the breeding-season. Very soon after they have left their breeding-stations, however, both old and young birds may be seen about the harbours and bays of Guernsey and the other islands seeking for food, in which matter they are not very particular, picking up any floating rubbish or nastiness they may find in the harbour. The generality of specimens occurring in the Channel Islands are in either winter or immature plumage, very few having assumed the dark-coloured head which marks the breeding plumage. This dark colour of the head, which is sometimes assumed as early as the end of February, comes on very rapidly, not being the effect of moult, but of a change of colour in the feathers themselves, the dark colouring-matter gradually spreading over each feather and supplanting the white of the winter plumage; a few new feathers are also grown at this time to replace any that have been accidentally shed--these come in the dark colour. The young birds in their first feathers are nearly brown, but the grey feathers make their appearance amongst the brown ones at an earlier stage than in most other gulls. The primary quills, which are white in the centre with a margin of black, vary also a good deal with age, the black margins growing narrower and the white in places extending through the black margin to the edge, so that in adult birds the black margins are not so complete as in younger examples.