THE SPRING MIGRATION 81 



these days we see the first individuals of such typical 

 summer species as the brown thrasher, towhee, whip- 

 poorwill, chimney-swift, and a few more of the war- 

 blers, especially the black-throated green, black and 

 white, and oven-bird. By the second week of May 

 everything is pouring in at once, and a list of arrivals 

 would include about all the small birds not yet men- 

 tioned. By the twenty-fifth of May most of the 

 birds which go farther north have passed on, the rear 

 of the procession being brought up by the blackpoll 

 in the opening days of June, though occasionally the 

 migration is greatly retarded when the season is cold 

 and backward. 



During the periods of migration there are some 

 things of value which may be learned, if students will 

 bear them in mind. For one thing we need to know 

 more of the effect of weather and storms upon birds. 

 Hence it is well to make note of conditions of 

 weather wind, approximate temperature, and pre- 

 cipitation in connection with the other observa- 

 tions. In time a series of such notes, especially from 

 many observers, would be of great interest and value. 

 Make record of birds killed by storms. Have an eye 

 out, too, as far as possible, for the directions in which 

 birds are seen migrating, their special lines of flight, 

 if any. From this we may gain new information as 

 to their movements. 



Birds do not always, by any means, migrate directly 

 north and south, as they are popularly supposed to do. 

 There seem to be certain " rivers " of migration, we 



