45 [Vol. xli. 



o£ the species on which they live, i. e., the amount of their 

 food ; consequently, it follows that between, say, 98-100 per 

 cent. o£ their progeny must be killed before the next breed- 

 ing season, and hence it follows with certainty that if one 

 artificially destroys, say, 50 per cent, of that progeny, 

 Nature^s toll of 98 per cent, of what is left is bound to 

 lead to a decrease of the species. 



Per contra, and just as surely, if we wish to preserve or 

 protect any animal, v/e have only to increase its output and 

 Nature does the rest, but in this case we must make sure 

 that the necessary food is also there. 



(i.) The easiest and most successful way is to have a close 

 time in the breeding season, thus preventing the adults 

 from being destroyed, and to reduce, if possible, their 

 enemies during that time. 



(ii.) To increase, if possible, their food-supply. Of 

 course, if we are protecting a species to destroy a pest, their 

 food is already present, and 



(iii.) To grow, plant, or otherwise make suitable breeding- 

 places. 



This last method may be of considerable importance, and 

 there is no doubt that in many places in England birds have 

 been induced to take up their quarters and stay to breed, 

 owing to artificial nest-boxes being placed on trees and 

 other suitable objects. Next in importance to their food is 

 this question of breeding-places, for during the nesting- 

 season many species will not allow another of their own 

 kind within a certain radius ; each pair having, so to speak, 

 an undefined kingdom, on which the intrusion of another of 

 its kind is violently resented, consequently the benefit of a 

 useful species becomes restricted if there are not enough 

 suitable and scattered breeding-places, in spite of the fact 

 that there may be a superabundance of food. 



Thus far I have dealt generally with the best methods of 

 increasing or decreasing species without reference to their 

 benefit or the reverse to man, and I have tried to show that 

 the protection of birds is not the best way of dealing with 



