128 ESSAYS OF A BIOLOGIST 



will have seen the Herring Gulls congregate in soar- 

 ing intersecting spirals where the cliff sends the wind 

 upwards. But such flights are nothing compared 

 with those of other birds. Even the staid black- 

 coated Raven may sometimes be seen to go through 

 a curious performance. One I remember, all alone, 

 flying along the side of a mountain near Oban; but 

 instead of progressing in the conventional way, he 

 flew diagonally upwards for a short distance, then 

 giving a special croak with something of gusto in it, 

 turned almost completely over on to his back, and 

 descended a corresponding diagonal in this position. 

 Then with a strong flap of the wings he righted him- 

 self, and so continued until he disappeared round the 

 shoulder of the hill half a mile on. It reminded me 

 of a child who has learnt some new little trick of step 

 or dance-rhythm, and tries it out happily all the way 

 home along the road. Mr. Harold Massingham has 

 seen the Ravens' games too, and set them down more 

 vividly than I can.^ He also is clear that they play 

 for the love of playing, and even believes that their 

 love of sport has helped their downfall to rarity by 

 rendering them too easy targets for the gunner. 



Or again, at the Egret rookery in Louisiana, at 

 evening when the birds returned in great numbers, 

 they came back with steady wing-beats along an 

 aerial stratum about two hundred feet up. Arrived 

 over their nesting pond, they simply let themselves 

 drop. Their plumes flew up behind like a comet's 



1 Massingham, '23. 



