274 KNOWING BIRDS THROUGH STORIES 



far before I was convinced that they had really started 

 southwards, for I did not hear the return signal and not 

 one bird showed the least disposition to circle or look 

 back. Gazing after them, I saw them meet the much 

 larger flock from Lemley's and all passed out of sight 

 over the southern horizon. 



These birds sometimes gather in large flocks for the 

 journey. Often all the purple martins within miles meet 

 at a common point, and together take their flight. The 

 departure is always in the morning and, as far as my 

 observation goes, before ten o'clock. 



Some naturalists claim that a few sentinels return to 

 the northland as early as the middle of March to spy out 

 the land and see if the old nesting places are in order. In 

 the southern part of the United States they are sometimes 

 seen in flocks of tens of thousands on the northward jour- 

 ney. At that time they move leisurely; but when spring 

 really comes in the north they usually appear at practically 

 the same time over a considerable area of territory and 

 begin nest building at once. 



If there are martins in your vicinity and you will con- 

 struct a proper house and mount it on a pole the day the 

 martins return to your neighborhood, you will very likely 

 find it inhabited within three or four days. Should you 

 put it up earlier than this, bluebirds are likely to take 

 possession of it before the martins come; once they are 

 in possession, the martins are not very likely to drive them 

 away. No bird is of more value to us human folks than 

 martins, not only because they drive away crows and 

 hawks, but because they feed largely on flies, ants, and 

 other injurious insects. 



Watch for the martins and learn to recognize them. 



