118 BIRDS OF THE WORLD 



Herring and Black-backed Gulls, which require years 

 to attain the adult plumage. See Plate 39, Fig. 228. 



During the winter months, for some years past, 

 these birds have assembled in large numbers on the 

 Thames and on the waters of the London parks. 



The Laughing Gull, which breeds in the eastern 

 part of North America, has in summer dark grey 

 wings and back, with black primaries, head and throat 

 darker, under parts white, and bill a deep red; in 

 winter, the head and throat become white, sometimes 

 streaked with greyish colour. The name is taken from 

 its curious cry, resembling laughter. 



The Black Skimmer or Scissor-bill is a remarkable 

 member of the Gull family, having the lower mandible 

 considerably longer than the upper. Both are thin 

 and very flexible, and the bird skims the surface of the 

 water in search of small aquatic creatures. These 

 birds are quite common along our southern coasts, 

 nesting in the sand and gravel of the beach.- The 

 young harmonise so perfectly with their surro-undings 

 as to be practically invisible. In them for some time 

 the mandibles are of equal length. The plumage of 

 the adult bird is black and white and the bill is red and 

 black. 



The small, fork-tailed, short-legged birds known as 

 Terns are very closely related to the Gulls, but have 

 relatively longer wings and are much more graceful 

 and swift in flight. They perform many strange evo- 

 lutions in the air, large flocks flying round and round 

 Ijin a huge circle, wheeling and swerving like one bird. 

 They are extremely noisy, uttering their harsh calls 

 almost continuously. Terns flap their wings much 



