38 



former with material derived from Grouse most of 

 them died within a very few hours and none survived 

 the fourth day. On the other hand no less than 

 thirty per cent, of the Sparrows either resisted 

 altop^ether or at any rate recovered ."^^ 



And so it comes about that while none are 

 absolutely immune, some species when brought into 

 captivity are said to be hardy or easily "acclimatized," 

 whereas others are regarded as " delicate." We often 

 see the expression that such and such a bird " when 

 thoroughly acclimatized is fairly hardy." What those 

 responsible for this opinion really mean — although 

 they are quite innocent of intending to convey the 

 impression— is that these particular species are so 

 susceptible to the effects of the special environment 

 attaching to captivity — not climate — that many or 

 most of them die, while certain individuals, being the 

 possessors of a special individuality, survive even 

 under the very adverse circumstances to which they 

 have become exposed. 



To illustrate the whole position in its various 

 bearings let us take the previously noted instances of 

 the Swallow and the Goldcrest, both " delicate " birds 

 as accounted in popular estimation. But in the case 

 of the former the "delicacy," or what would be called 

 the '* difficulty of acclimatization" if it were purely a 

 foreign bird, lies principally in the necessity which 

 exists for persuading him to alter his ancestral 

 mannerf of feeding. A bird which for countless 

 generations has fed only on the wing by opening a 

 wide and gaping mouth, which more or less auto- 

 matically engulfs its prey, is not to be easily taught 

 to pick up its food from the floor. In those cases, 



•Klein. Etiology afid Pathology of Groiise Disease. 1892. 

 t John Hunter, F.R.S. Essays and Observations on Natural History, 

 Prof. Owen's edition. 1861. Vol. II., page 280. 



