S I R S , -- I have often been struck by the apparent differences in colour of Lesser Black-backed Gulls on the Clyde. On May gth, 1936, a t 9.30 a.m. (summer time) I watched half a dozen of these Gulls sitting on a railing on Dunoon pier within a few yards of me. The railing was so placed t h a t the Gulls were turned either directly to the sun or directly away from it. Those facing the sun appea...

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