450 THE GANNET 



for what else is there which can make up to them for their 

 extraordinary liabiUty to accidents, or compensate them for 

 the mortaHty which takes place among their young ? — a 

 mortality far greater than that which befalls human 

 beings. Especially would it be in accordance with the 

 rule of Nature, that a bird like the Gannet should be 

 long-lived, because here we have a species which does 

 not breed until it is three years old, and then only 

 once a year, laying a single egg. It seems only reason- 

 able to conclude that birds laying a single egg should 

 have some advantage over birds which lay a great many 

 — this is a compensation which we should expect Nature 

 to provide. It is but natural to infer that Gannets 

 would be longer lived than Ducks, Partridges, Pheasants, 

 or Titmice, which begm to breed when one year old, 

 and which lay a great many eggs. In fact, the only other 

 way in which the difference between them could be adjusted 

 is by assuming a much greater mortality among the young 

 of Ducks and game-birds. Something there must be to 

 account for the relative proportions of the numbers of 

 these birds remaining the same, and that something must 

 be either age or a difference of mortality between them. 

 It is not very easy to say which are short-lived species 

 and which are not, but observations taken in Norfolk lead 

 me unhesitatingly to class the Partridge {Perdix cinerea) as 



