THE SOUTHWARD FLIGHT 271 



and South Africa ; while a still greater distance is travelled 

 by several species of waders which breed in the far north of 

 the Russian Empire or in Greenland, and winter as far south 

 as Cape Colony. Some of these birds, such as the little 

 stint and curlew-sandpiper, occur in Britain only as 

 passengers for some weeks in spring and autumn, on their 

 way between their southern and northern homes. Other 

 species, such as the knot and sanderling, are also winter 

 visitors. Most of them haunt the sea coasts, especially the 

 oozy estuaries, which supply them with the most extensive 

 feeding-grounds. But a typical bird of double passage, often 

 seen along inland streams in spring and early autumn, is the 

 green sandpiper. It can be easily distinguished from the 

 common sandpiper with a fieldglass, or even with the naked 

 eye, by the tail being transversely barred with white, instead 

 of being merely edged with it. The green sandpiper nests 

 in the Baltic and Arctic basins, and winters in Africa and 

 southern Europe. 



As birds which cross the equator on either passage 

 secure two summers in each year, and no winter, there 

 seems no reason why our birds should not breed twice 

 a year, once in either hemisphere. But all the most 

 trustworthy evidence at present indicates that they nest 

 only in the northern hemisphere ; no certain case has 

 yet been reported of any bird which nests in summer 

 in the far north of Europe or America also nesting 

 in South Africa or South America. Some of these birds 

 of double passage are believed to travel as much as 

 eleven thousand miles in each direction annually. From 

 these vast journeys the scale of distances traversed on 

 migration descends to the few yards which part the nesting- 

 quarters of a robin or pied wagtail in the shrubbery or by 

 the farmyard pond from its winter haunts in the sheltered 



