Juvenile and winter plumages of the Marsh terns

Migration Research Officer, B.T.O. (Plate 36) I D E N T I F I C A T I O N of the three British marsh terns (Chlidonias spp.) outside the breeding season has long constituted a problem for the bird-watcher. There is a cautionary note in The Handbook of British Birds (vol. v, pp. 7 and 9) to the effect that the Whiskered Tern (Ch. hybrida) and White-winged Black Tern (Ch. leucopterus) are probably n...