OF SOUTHERN AUSTRALIA. 43 



Migration may be complete, partial, or accidental. In 

 the case of the Swifts, which pass through the summers of 

 both hemispheres, it is complete. The Welcome Swallow, 

 journeying antmally between Queensland and Tasmania on 

 the eastern side, offers a good example of partial migration ; 

 whilst the European Shoveller Duck, which wanders to our 

 continent occasionally, presents a case of accidental migra- 

 tion. 



It was generally believed by people living in the time of 

 Gilbert White, of Selborne, that Swifts and Swallows buried 

 themselves away in ponds and mud pools during the winter, 

 which they passed in a state of torpor, from which they were 

 awakened by the advent of spring. It was discovered later 

 by observers that they wandered to other lands, attracted 

 thereto by the abundant food of summer. Finally lines of 

 flight across certain countries were mapped out. For genera- 

 tion after generation, extending probably through thousands 

 of years, these paths had been followed by the migrating 

 birds, who, guided by old travellers or by an unerring instinct, 

 deviated little from the line, excepting under stress of 

 weather. 



