ITS DEVASTATIONS. 141 



feeder ; and it may be questioned whether, if it 

 had not recourse to its extraordinary plan of 

 taking care to monopolise all the food to itself, the 

 birds would be capable of rearing it up together 

 with four or five querulous nestlings in addition. 

 The lives of the latter are, therefore, sacrificed to 

 the preservation of the one life of the former. 



The destruction of eggs and young thus com- 

 mitted must be excessive, even in a single year. 

 Mr. Blackwall has made some ingenious calcula- 

 tions, which give something of an idea of its 

 amount. He says, the mean number of eggs laid 

 by those birds that are usually selected by the 

 cuckoos to provide for its progeny, is five. Now, 

 the area of England and Wales may be taken at 

 49,450 square miles, which, reduced to square 

 yards, gives 153,176,320,000. This, divided by 

 3,301,816 square yards, the area of the township 

 of Crumpsall, and the quotient multiplied by 3, 

 the mean number of female cuckoos for every 

 3,301,816 square yards, gives 139,173, the mean 

 annual number of female cuckoos that visit England 

 and Wales. This sum multiplied by 5, the mean 

 number of eggs laid by the cuckoo, gives 695,865, 

 the number of nestlings produced annually by the 



