PHASES OF SOCIAL LIFE 139 



only wonder how those clinging to the bough manage to 

 sustain the weight of their fellows for so long a time. By way 

 of corroboration we may remark that the Mouse-birds or Colies 

 also sleep after this fashion. 



This reversed position during sleep, by the way, is still more 

 marked in the little Hanging Parrots. Numbering some twenty 

 species, and ranging from India and the Philippine Islands, 

 through the Malayan region as far east as Duke of York Island, 

 these little birds, which do not exceed five inches in length, all 

 share the habit of sleeping suspended by their feet from the 

 under surface of the bough, hanging for hours at a time head 

 downwards, after the fashion of bats. Not only during sleep, 

 however, do they thus hang, for in confinement they will 

 so hang crowding together and caressing one another after the 

 fashion so common among Parrots. 



The good comradeship displayed in these curious sleeping 

 communities is exhibited in other directions among birds, and 

 especially in the co-operation many display in the capture of agile 

 prey. Thus the Golden Eagle {Aquila chryscetos) will some- 

 times at any rate hunt in concert for game. On such occasions 

 one bird glides over the ground beating the bushes and under- 

 growth with its wings, while the other remains on the lookout at 

 a slight elevation, pouncing at once upon whatever game is driven 

 out, and sharing with its companion. Similarly, Pelicans, when 

 fishing in a lake or bay, combine to form a semicircular cordon, 

 driving a shoal of fish before them to the bank. As soon as they 

 have succeeded in getting their victims sufficiently massed they 

 set about reaping the fruits of their shepherding, filling their 

 large pouches as one might fill a landing-net. Cormorants are 

 said, occasionally at any rate, to adopt "similar methods of 

 hunting. 



Gregarious habits are, as we have seen, fostered and devel- 

 oped where the food supply is unlimited ; but wherever a suf- 

 ficiency is obtainable only by strenuous hunting, segregation and 

 competition result. These factors, however, are not so obvious, 

 and cannot be seen at work as the opposite to this picture can be 

 seen. Flocks of birds feeding in harmony impress us : those 

 that lead solitary lives escape our attention, and the fact that 

 this isolation is more or less enforced does not easily admit of 

 demonstration. As a rule, probably, it is taken for granted that 



