QUEENSLAND and NORTHERN TERRITORY 35 



have four in Australia, and the colours throughout 

 the family are blue, green, vivid scarlet, yellow, 



purple, black and w^hite. 



DISTRIBUTION OF SWIFTS AND 

 SWIFTLETS IN AUSTRALIA 



Tasmania is the southern limit and winter home 

 of two species of swifts (map 12). Of these the 

 "fork-tail" nests in Yakutsk, the centre of the 

 extensive fur trade of central Siberia, while the 

 "spine-tail" nests in Japan, Manchuria and Chosan 

 (Korea). 



The swiftlets live mostly in the Malay Archi- 

 pelago about the Gulf of Carpentaria and the north- 

 eastern coast of Queensland. Convergent evolution 

 applies to swifts and swallows, while an examina- 

 tion of the hand and arm of each shows them not 

 to be at all related. The swift has a long hand 

 and a short arm, the swallow the opposite. 



The Swifts are remarkably fine fliers and great 

 insect eaters : feeding while on the wing. Their 

 work is to reduce the swarms that spend the adult 

 period of life high in the air. It is a fine provision 

 of nature for certain species to feed on one plane 

 and others elsewhere. A law for prevention of 

 overlapping is found among the pasture feeding 

 birds and the bush birds. Each pair patrols its own 

 area in nesting season. 



The swifts work through the law of mutual aid 



