XXX. THE GANNET 



that : "If every pair of sparrows alive in London at the 

 beginning of the breeding season displayed maximum 

 fertility, a death-rate of about 90 per cent, per annum 

 would be necessary to keep the sparrow population 

 stationary " (" Proceedings of the Zoological Society," 

 1911, p. 426). This is no exaggeration of the case, and 

 what apphes to the House-Sparrow applies in a less 

 measure to the Gannet. Charles Darwin has touched on 

 this subject with his usual perspicuity : " Every organic 

 being," he says, " naturally increases at so high a rate, that 

 if not destroyed, the earth would soon be covered by the 

 progeny of a single pair." (" The Origin of Species," 1st 

 ed., p. 64). See also his illustration of this proposition 

 in the case of that familiar household bird, the Robin, in 

 " Foundations of The Origin of Species " (p. 89). 



Connected with the question of Gannet mortality, 

 although in no way explanatory of it, is that of the average 

 age to which Gannets live, and tliis is a matter in which 

 the more we can get away from the region of guess-work, 

 the more chance there is of arriving at something definite 

 about a subject which has baffled scientists from the 

 days of Lord Bacon. Some very imperfect remarks 

 have ])een made about it in Chapter XVIIL, to which 

 I need not again refer. In this connection there is one 

 point which has to be remembered, Gannets are very liable 

 to accidents, even after they have passed the first six critical 

 months, as has been shown in Chapter XVII. The per- 

 centage of Gannets which groAvs up, attains maturity and 

 ultimately dies a natural death, must be exceedingly small ; 

 I doubt its being one per cent. ; but then it may well 



