114 



THE AGRICULTURAL NEWS. 



April 16, 1910. 



however, another, particular view of the case which 

 has its origin in the dangers that attend the 

 making of such introductions. These are sufficiently 

 serious, as will be shown later, and their existence 

 leads back to the original question of what can be 

 done, in the case of a given country to conserve the 

 useful birds that are already found there. 



In arriving at a conclusion as to the expediency of 

 obtaining a species from another country to do the 

 work of keeping down insects, the first attention will 

 be given to its behaviour in its native land. It will 

 naturally have had attention drawn to it by the good 

 that is effected by it, but this view must not obscure 

 the need for thorough investigation of its habits, in 

 order that the presence of any untoward traits in its 

 character, which might develop under changed condi- 

 tions, may be discovered. One of the greatest of such 

 changed circumstances will be that, most probably, its 

 natural enemies will be absent from the country to 

 which it is taken, with the result that the increase in 

 numbers that is permitted will necessitate a change in 

 the nature of the food, and the bird may develop fruit- 

 eating or grain-eating habits to such an extent as to 

 become a pest to agriculturists. It is in this connexion 

 that the importance seems to be indicated of the 

 possession by all colonies of stringent laws regulating 

 the introduction of animals of every kind, so that this 

 would only take place, in the case of any given species, 

 after thorough consideration of its advisability, under 

 the advantages of expert assistance. 



The greatest care is required in examining both 

 native and introduced birds for the purpose of deter- 

 mining if they possess feeding habits which will 

 be of benefit to the agriculturist. Such an investiga- 

 tion, if it is to give trustworthy results, must not be 

 confined to one season of the year or to one set of 

 climatic and local conditions. Observations have shown 

 Ihat birds of various kinds show more adaptability to 

 different foods than is generally recognized, and that 

 if they are driven by stress of circumstances to adopt 

 a vegetable diet, they do not necessarily continue such 

 feeding habits when the restoration of normal condi- 

 tions takes place. The adverse conditions may be 

 temporary for climatological reasons, or permanent, 

 from local ciuses, and it is manifestly unfair to 

 make conclusions about the feeding habits of 

 a species until it has been examined under as 

 wide a variety of conditions in time and space as 

 is possible. A fair investigation of this description 

 will probably show, in many cases, that the ability of 

 a bird to subsist on vegetable food for a time is a char- 



acteristic in its favour, rather than against it, for it 

 merely takes a temporary toll from the agriculturist, 

 in order that it may survive to do the work that he 

 expects of it, in the future. A fuller recognition of 

 these facts would probably end much of the confiicting 

 evidence that is obtained when enquiries as to the 

 usefulness or otherwise of a given species are made. 



After due attention has been paid to all these 

 considerations, it may be decided that it is expedient 

 to assist the useful native birds in the work of the 

 destruction of insects by bringing in others which have 

 similar feeding habits. This decision calls, again, for 

 caution, in another way. The insect population of 

 an island is subject to large fluctuations — a face that 

 is brought home to every agriculturist, sometimes in 

 an unpleasant manner. There is also the fact that the 

 food-supply per head is reduced by the advent of the 

 new-comers. The possibility has therefore to be faced 

 that, owing to the competition arising from the reduced 

 amount of food, the native birds of the island, which 

 once served a useful purpose, will be driven to subsist 

 to an increasing extent on fruit and other agricultural 

 products, and may in the end do more damage than 

 the insects which it was desired to control. 



The facts that have been brought forward will 

 serve to show that great risk attends the introduction 

 of new species of birds into a country, and that it is 

 difficult to gauge the ultimate effects that may 

 result from their presence. This leads to the sug- 

 gestion of another precaution, namely, that these birds 

 should, if possible, possess a period in their life-history 

 during which their habits are such that they can be 

 destroyed with comparative ease; for instance, the pur- 

 pose will be served if the nests are made in accessible 

 positions, so that either the breeding birds, the eggs or 

 the nestlings may be taken. It may be argued that 

 the existence of this very circumstance will operate 

 against the acclimatization of the bird, owing to the 

 chance that it gives for its destruction by enemies. 

 This is actually the case, but the proper regulation of 

 the conditions under which it is introduced should 

 enable it to reach such numbers as to prevent the 

 possibility of its extermination in that way. 



From past experience in the West Indies, it 

 appears that the establishment of a species of bird in 

 a new habitat is by no means a simple matter, and 

 several failures have been recorded. In the light of 

 this, it would seem that, especially in the case of grega- 

 rious birds, they should be imported in large numbers; 

 that several importations, at fairly short intervals, 

 should be made; and that there should be provision for 



