CHAPTER II. 



INCUBATION CONTINUED. 



HITHERTO we have seen the process of natural 

 incubation carried on by means of the natural 

 warmth of the mother's breast alone. And this is 

 the almost universal method in nature. But a 

 most remarkable exception to the general rule has 

 been discovered in Australian ornithology. It has 

 already been noticed, that it appears probable in 

 a few instances, and under the pressure of any ex- 

 traordinary circumstances, that birds will for a time 

 leave their nests, as if sensible that the external 

 temperature was sufficient to carry on the process 

 of incubation during the period of their temporary 

 absence: the instances of the fly-catcher in the 

 conservatory, and of the ostrich, illustrated this 

 observation. We are now, however, to notice 

 the proceedings of some birds who commit the 

 whole business of incubation to external cir- 

 cumstances ; adopting, however, a most ingenious 



