130 BIEDS 



problem of feeding many mouths with little food by be- 

 having like competing business men. Migrate do I say? 

 A euphuism for bolting. They do worse, for they 

 actually combine rather than compete when food is scarce. 

 The phenomenon of winter flocks composed of a variety 

 of species and all co-operating in the hunt for food is 

 most unfriendly evidence for the specialists and a most 

 unfratricidal act of the members of the flock towards one 

 another. And there was that horrid disillusionment about 

 the black and the brown rat. The latter ought to have 

 exterminated the former ; he owed it to the competition 

 theorists. It was almost their only solid ewe lamb, for 

 alas, the famous warfare between kindred has turned out 

 to be one of those phantom wars one reads of in the Norse 

 Edda. 



SOCIAL NESTING 



Among the many nests built annually by house-martins 

 under the eaves of our house I frequently notice double 

 ones like the one mentioned by your correspondent last 

 week and this year I see there is a treble one in which 

 three flourishing broods are being brought up. 



VERONICA S. BATCHELOR. 



July 15, 1911. 



NOTE. Miss Clemence Acland sends an account of a 

 double nest of martins and a fourfold one of rooks, with 

 a single outer wall, to the same issue of the Spectator. 

 These experiments remind one of the more highly 

 developed social adjustments of the weaver birds of South 

 Africa (see Houssay, " Industries of Animals "), who 

 construct, each pair, their private cottage under the shelter 

 of the umbrella thatch built by the little architects in a 

 body. Evidence of this kind is of deep interest to 

 naturalists, because the individualism of the nesting 

 season with its appropriate physiological stimuli is nearly 



