NEW SOUTH WALES 75 



sentatives of the three great zoological sub-regions 

 of Australia proper, as shown in Map 29. 



Then there is the annual migration of these 

 species from any one of these sub-regions into a 

 second one, to the extent that birds of the Bassian 

 sub-region, in the northern portion, pass northward 

 to winter in northern New South Wales (Eyrean 

 sub-region). This is while they pass from the 

 southern Eyrean (N.S.W.) into the northern 

 Eyrean (Queensland) to winter. 



A third horizon of interest is the Bathic (map 

 29, 30), the passing of lowland birds into the area 

 of 5,000 ft. to 7,000 ft., to nest in summer snow 

 storms. Apart from this we see from time to time 

 — two to seven years — sporadic migration on a 

 large scale. 



And we have the birds purely local in the dry 

 Eyrean, as well as those local in the moist Bassian 

 forests. 



It may be said in the matter of extension of dis- 

 tribution that a species of bird has : — 



A — A portion of the continent in which to winter 

 B — A portion of the continent in which to summer. 

 C — A portion of the continent in which to summer 

 and to winter (local). 



It is very much dependent on the season and 

 local food supply whether or not a species will 

 extend its area for that season, or a cycle of years. 

 Such a bird as the Magpie, coming under neither 

 A nor B is constant to its stretch of country the 



