THE BIRDS 



419 



that gives them their name. One of their most interesting achievements 

 is their ability to remain motionless in mid-air. When doing this the 

 wings vibrate so rapidly that they cannot be seen, and it appears as if a 

 wingless bird is suspended in space without any visible means of support. 

 Since even their tiny bodies would be too heavy for most flowers, this is 

 an adaptation for their nectar-sucking habits. They suspend themselves 

 in the air while thrusting their long bills down in the flower for a drop of 



Photo by R. Martin Perkins 



Fig. 27.10. Ruby-throated hummingbird. Although the hummingbird is the smallest 

 of our birds it is almost fearless, seeming to have confidence in its speed and maneuver- 

 ability as a means of escape from enemies. 



sweet nectar. A jar of sugar-sweetened water outside a window sill may 

 attract these friendly little visitors for close observation. Small as they 

 are, they are among the most fearless of birds, evidently feeling confi- 

 dence in their speed and maneuverability to escape at a sign of danger. 

 The Ostrich. While we are dealing with extremes we might men- 

 tion the largest of the living birds. The ostrich may be more than eight 

 feet tall and weigh up to 300 pounds. It uses only two toes which are 

 covered with broad pads and are well adapted to travel in the desert. 



