150 CHARLES DARWIN 



quite smooth, and it formed a most curious spectacle to be- 

 hold a flock, each bird leaving its narrow wake on the mir- 

 ror-like surface. In their flight they frequently twist about 

 with extreme quickness, and dexterously manage with their 

 projecting lower mandible to plough up small fish, which are 

 secured by the upper and shorter half of their scissor-like 



bills. This fact I repeatedly saw, as, like swallows, they 

 continued to fly backwards and forwards close before me. 

 Occasionally when leaving the surface of the water their 

 flight was wild, irregular, and rapid; they then uttered loud 

 harsh cries. When these birds are fishing, the advantage 

 of the long primary feathers of their wings, in keeping them 

 dry, is very evident. When thus employed, their forms re- 

 semble the symbol by which many artists represent marine 

 birds. Their tails are much used in steering their irregular 

 course. 



These birds are common far inland along the course of 

 the Rio Parana ; it is said that they remain here during the 

 whole year, and breed in the marshes. During the day they 

 rest in liocks on the grassy plains at some distance from 

 the water. Being at anchor, as I have said, in one of the 

 deep creeks between the islands of the Parana, as the even- 

 ing drew to a close, one of these scissor-beaks suddenly ap- 

 peared. The water was quite still, and many little fish were 

 rising. The bird continued for a long time to skim the 

 surface, flying in its wild and irregular manner up and down 

 the narrow canal, now dark with the growing night and the 

 shadows of the overhanging trees. At Monte Video, I ob- 

 served that some large flocks during the day remained on the 

 mud-banks at the head of the harbour, in the same manner 

 as on the grassy plains near the Parana; and every even- 



