11 



In the earlier days of Hobart Town dense scrubs extended 

 down the courses of the rivulets from Mount Wellington 

 close to the town, and these scrubs were inhabited by large 

 numbers of predaceous birds, now almost wholly absent. I 

 allude to the large Chestnut-faced Owl (Strix castanops), the 

 small spotted Owl (Spiloglaux maculatus), the Owlet Night-jar 

 {j^gotheles Novcd HollandicB) and the Mopehawk {Podargus 

 Cuvieri). Till within the last few years these birds scoured 

 the open country in their immediate neighborhood every night, 

 the three last for insects, and the first for insects, birds, and 

 small mammals. With the destruction of their daily hiding 

 places these night-birds have gradually disappeared, and the 

 insects on which they fed have proportionately increased, 

 offering, I have little doubt, tempting inducements to the 

 Magpies and other insectivorous birds to extend their range 

 over the ground heretofore scoured by the night-feeders. 



This alone may possibly account for the gradual introduc- 

 tion of the Magpie, and probably had a direct influence on 

 the Miners and Rosellas, for both the latter birds are occa- 

 sionally torn off their roosts by the large Owls, in the stomach 

 of one of which I once found the greater part of a Magpie. 



If I am right in my supposition as to the cause of the 

 gradual appearance of these birds in country hitherto unoccu- 

 pied by them, and that it takes so slight a change in the 

 natural balance of creatures to settle the question of presence 

 or absence of particular forms of life, it behoves all those 

 interested in the cause of acclimatization to study well the 

 natural history and capabilities of the countries to which they 

 wish to introduce new creatures before spending much time 

 or much money in their experiments. Wherever the de- 

 struction of indigenous creatures has been carried to such an 

 extent as to amount virtually to extirpation, the acclimatizer 

 may do good service in introducing and protecting animals 

 of similar habits to those driven out, but where no such 

 extirpation has taken place we may rely upon it that the 

 successful establishment of new creatures can only be accom- 

 plished at the expense of those already in possession of the 

 ground, and we should therefore be especially careful that 

 the forms to be introduced are better worth having than 

 those already existing. 



With regard to the vegetable kingdom, if a man wishes to 

 establish new plants he first proceeds to clear his ground of 

 the existing vegetation, and would consider the attempt 

 useless without this precaution. Is it not more than probable 

 that the same natural laws, in this instance, govern both the 

 animal and vegetable kingdoms ? 



