294 BULLETIN 191, UNITED STATES NATIONAL MUSEUM 



Stream of birds breaks up again into groups and parties, and after one 

 or two preliminary circlings the birds pour down into the trees with a 

 renewed crescendo of cawings and other strange noises before finally 

 settling down for the night. 



The aerial evolutions referred to afford as impressive and exciting 

 a spectacle as an ornithologist can wish to see and reveal an agility and 

 a capacity for frolicsome behavior that are not a little surprising in these 

 usually sedate birds. They plunge and dive headlong from a great 

 height, roll, tumble, sideslip, and chase one another in swerving and 

 switchback flights like a veritable avian circus troupe. Such displays, in 

 which immature as well as adult birds participate, are not confined to 

 roosting time, but may be seen also earlier in the day, especially in 

 September. As mentioned under "Courtship" something of the same 

 kind may also be observed in spring, but it is much more characteristic 

 of the fall. It is an expression of a sort of general joie de vivre without 

 sexual significance, and if the scientist needs to classify it somehow it 

 must be reckoned as a form of social, not sexual, behavior. 



Allusion has been made above to visits to the rookery during the period 

 under discussion. Though occurring, especially, early in the morning 

 soon after daybreak and late in the afternoon they are by no means con- 

 fined to these times, for the birds often feed close to their breeding 

 places and pay visits to the trees during the day. As the season ad- 

 vances these visits become more frequent and more prolonged, and 

 early in the year signs of a renewed interest in building and nest repair 

 may be observed, as already described, but the winter roosts are not 

 generally abandoned till about mid-March. The mode of abandonment 

 seems to vary ; it may apparently take place all at once or be spread over 

 some days up to ten or more, but sooner or later the birds are all 

 roosting again at their own rookeries and the annual cycle begins once 

 more. 



DISTRIBUTION 



TAcknowledgment is made of assistance derived in the compilation of this sec- 

 tion from the sections on "Distribution Abroad" by F. C. R. Jourdain and on "Mi- 

 gration" by N. F. Ticehurst in the Handbook of British Birds (1938).] 



Breeding range. — Occurs throughout the British Isles wherever there 

 are trees for it to breed in, but not in the Shetlands. Breeds in greater 

 part of Continental Europe from latitude 635^° N. in Norway, 60° in 

 Sweden, 62° in Finland and northern Russia, east to Perm (eastern 

 Russia) and south to mid-France, northern Italy, Serbia, Bulgaria, and 

 southern Russia. Allied races are found in west temperate and eastern 

 Asia. 



Winter range. — Breeding birds are sedentary or mainly so in tern- 



