86 THE MIGRATIONS OF BIRDS 



blue] ays that is unquestionably a migration to some 

 winter range. Similar flights have been recorded at 

 other points, and it is hoped that eventually records 

 from banded birds may throw some light on its 

 extent. So far as observed this movement is diurnal, 

 and I have seen no indication of night flight in this 

 species. The course pursued at Washington is to- 

 ward the south and southwest, and the steady pas- 

 sage of birds, flying from 50 to 150 yards from the 

 earth, is as noticeable as the migration of sharp- 

 shinned hawks that often takes place at the same 

 time. 



Washington also marks a point near the northern 

 extension of the southern subspecies of the common 

 crow (Corvus brachyrhynchos paulus) , a form marked 

 by small size, that ranges from Alabama north to 

 southeastern Kansas, Maryland, and Virginia. In 

 winter we have an influx of the larger northern bird, 

 which arrives in flocks, and which, until disturbed 

 by building operations in suburban development, 

 formed great roosts within the limits of the District 

 of Columbia itself. With the opening of spring 

 weather in March the resident birds begin the aerial 

 gyrations and the peculiar calls that mark their 

 pairing and mating. I have watched these mating 

 evolutions among birds circling over low hills near 

 the Potomac River, while on the tide-flats below I 

 had before me scattered flocks of the northern birds 



