422 PASSEKINE BIRDS. 



length of tlieir wings. They are divided into Swallows, properly so 

 called, and Swifts ; the latter are known by a remarkable conforma- 

 tion of their feet, the thumb is directed forward like the other 

 toes, which are all separate, and each has but three joints, while 

 in the Swallows the thumb points backwards, as in the other Pas- 

 serine. 



The Swallows, properly so called, have a triangular beak, the legs 

 short, the wings very long, and the tail usually forked. They de- 

 light in places where flies and other insects are common ; they 

 construct their nests witli great care, sometimes in the ground. 

 Most of the Swallows leave us in September, and migrate in large 

 flocks to warm countries, where they pass the winter ; tliey return in 

 the beginning of spring, and take possession of the nests they had 

 left the preceding year. Their habits are mild, and they are re- 

 markable for their sociability. They often join together in great 

 numbers to drive ofl' an enemy, the attack of which any one of them 

 may fear. The Swallow announces, even to the Swifts and other 

 small birds, the approach of a bird of i^rey. At the sight of an 

 Owl or a Hawk, it utters a piercing cry ; immediately all the birds 

 of its species and the Swifts assemble roinid it, and often fly in 

 phalanx 'against the enemy, which they harass until he is forced to 

 retreat. 



'I'he Swifts (Choetura, Cypselus)]iQ,\e a forked tail, and surpass even 



the Swallows in their powers of Ihglit ; in fact, they scarcely walk at 

 all, and are seen conthmally in flocks, pursuing insects in the upper 

 regions of the atmosphere with loud cries. They nestle in holes 

 in walls and rocks, and climb along smooth surfaces with facilitv. 



