8o THE BIRDS OF 



pose in every way. They have long 

 wings, so that they can sail through the 

 air for long periods without fatigue. 

 Their feet are very tiny and weak and 

 are rarely used by the birds for walking, 

 as they prefer flight whenever possible. 

 Unlike most perching birds, Swallows 

 migrate by day. 



The Tree Swallow (Plate 22, p. 151) 

 is silky-white below and shining em- 

 erald-green above. It is termed the 

 White-bellied Swallow by some authors. 

 Tree Swallows are among the first 

 to arrive from the South in the spring 

 and the first to depart in the fall, though 

 some linger late in the season. As 

 early as the first of July they gather 

 in flocks and at night roost in marshes. 

 They raise two broods of young a year. 

 The Tree Swallow may sometimes be. 

 told from the Cliff and Barn by the 

 fact that this bird prefers to fly high in 



