VICTORIA 117 



THE EFFECT OF THE DIVIDING RANGE 



As we come south from the warm moist air of 

 the Hawkesbury River in New South Wales, we 

 may observe that the colour of all the birds of any 

 any one species is growing darker (map 48, a). 

 That is the climatic effect on the plumage. Having 

 followed this change as far as Port Phillip, and 

 continuing westward, we less readily see a second 

 change, b. It is the western drier light air influ- 

 ence. The grass and the trees have all accepted 

 the changed weather conditions, and taken on an 

 altered dress. 



North of the Dividing Range, c, there is a larger 

 mass of migratory birds than in the south, e.g. the 

 chats (Ephthianura), one red, the other yellow. 

 When meeting the mountain bar the food becomes 

 less, and many birds considering they have come 

 far enough southward, stay and feed and nest. The 

 lesson of many generations, extending over many 

 centuries, is to come south to the same areas, each 

 to its kind. 



The present day species, incoming with the 

 spring, make for the old nesting grounds. If the 

 previous season has been a dry one, and seeds and 

 insects are in small supply, many birds will cross 

 over the smaller hills and relieve the strain on the 

 food supply in the usual nesting grounds. It is 

 then that naturalists will record strange birds being 



