328 The Bird 
and is often so characteristic that when too far off to dis- 
tinguish the colour of its plumage, or for its notes to 
reach our ears, the bird may be recognized by the undu- 
lations or the directness of its flight. No one who has 
ever visited the tropics can have failed to admire the 
Fig. 263.—Wing of living Herring-gull; long and narrow for slow, 
continuous flight. 
soaring vultures,—spots of black swinging across the 
heavens or swooping low in grand ares over the palms. 
Gulls and their kindred fly steadily with continuous wing- 
beats, which, however, are much less rapid than in the 
flight of a duck or a parrot. Many sparrows have an 
abrupt jerking motion, hitching themselves over trees 
