NOTES. 223 



have seen five eggs fairly often in clutches laid in late June 

 and early July, in Norfolk and Sussex, when food is very 

 abundant. 



Norman Gilroy. 



Further to my note on this subject (antea pp. 198 and 199) 

 I am quite aware that some authors attribute the large 

 clutches of eggs laid by the Rough-legged Buzzard, Snowy 

 Owl, and other birds, to the abundance of food, more 

 especially to the lemming, but in the absence of any concrete 

 evidence to verify this suggestion, I am led to believe that an 

 error has been made. To my mind, it is obviously wrong and 

 contrary to the rule of nature. However, I am collecting 

 evidence, and, so far, the onus of proof is certainly against the 

 theory. On the return of my Scandinavian correspondent 

 from Siberia, I hope with his assistance to prove my point 

 conclusively. 



Percy F. Bunyard. 



The recent correspondence on the subject of the number of 

 eggs laid by the Arctic Tern has introduced the much wider 

 and more important subject of the relation between the food- 

 supply of a given species and its powers of reproduction. Mr. 

 Jourdain has referred to the well-known case of the Baptores 

 in Scandinavia having exceptionally large clutches of eggs in 

 the years when the food-supply is unusually plentiful, and 

 cites the writings of Professor Collett and Mr. H. J. Pearson 

 in corroboration. Of the facts there cannot be the least doubt, 

 they have been confirmed over and over again, and in the 

 case cited it may well be an instance of direct cause and effect. 

 After my personal experience of a "lemming year" in 

 Norway, I, for one, should be exceedingly reluctant to dis- 

 believe the direct relationship of food-supply and increased 

 fecundity. On the other hand I do not feel at all sure that 

 even in the case above-mentioned we have the whole explana- 

 tion, for regard must be given to the undoubted fact that this 

 increase of reproductive powers in certain years in Scandinavia 

 is not confined solely to the lemmings and the birds that 

 prey upon them, but affects simultaneously many other 

 species. I could quote several instances of this from my own 

 observations, and Professor Collett makes repeated reference 

 to it in his writings ; thus in his monograph on the lemming, 

 he gives many instances of this simultaneous increase of 

 fecundity amongst not only other small Mammalia, including 

 the hare, but such widely-separated forms as the Baptores, 

 the game-birds (Ptarmigan, Willow-Grouse, Blackgame and 



