BRITISH GENERAL MIGRATORY MOVEMENTS 593 



flight." Whether it is wise to say " impossible " in the face of evidence which we possess of the 

 journeys of the American golden-plover and other waders, is open to question ; l but with regard 

 to the majority of the American visitors it is evident that they made an error at the start, and 

 probably joined some band of south-eastward bound regular migrants instead of travelling with 

 their own kind in a south-westerly or southerly direction. Wind may drift birds from their 

 normal pathway at any point on their passage, and this fact probably accounts for the frequent 

 occurrence of ordinary east-coast birds of passage on our western seaboard and in Ireland. It 

 is, however, a fact that the west-coast passage has received less attention than that on the east. 



The question as to whether a bird is out of its course or on its ordinary route depends 

 largely upon how far the existence of direct migration pathways is admitted, or how wide or 

 narrow these pathways are believed to be. In some autumns certain species are more abun- 

 dant on passage on the east coast than in others ; this applies to regular visitors like the grey- 

 crow, shore-lark, and brambling, as well as to rarer " vagrants." Either the numbers of these 

 birds are subject to great fluctuations or they only travel by this route in some seasons. 

 Others of the same species are known to voyage along the eastern borders of the North Sea, 

 and it is probable that the numbers which take one passage or the other are regulated by the 

 direction and force of the wind at the time of departure, deviating the stream to one coast or 

 the other. The arguments that the direction of the wind has no influence at all upon the birds, 

 but that force alone acts as a stimulant or deterrent, are not convincing. The route in this 

 case is the whole of the North Sea, but most of the travellers move along one or other side- 

 track, where they may obtain food and rest, rather than brave the dangers of the central 

 landless roadway. 



Lastly, there are a number of petrels, shearwaters, and other pelagic birds, nesting in some 

 cases in the South Atlantic or even Pacific, which have wandered into the North Atlantic and 

 been recorded for Britain. These birds have hardly found their way to our shores, they have 

 lost their way until they found themselves stranded here ; their casual wanderings have little 

 association with true migration. With a few it is different ; the great and sooty -shearwaters, 

 for example, are regular northward migrants in the autumn ; they wander in search of food 

 from their southern breeding haunts in exactly the opposite direction to the Arctic-tern, which 

 from its arctic and northern home, which has a southern limit in our islands, travels during our 

 winter so far as the Antarctic. The explanation is very simple ; these two shearwaters, and 

 some others which come more rarely, are birds of the southern hemisphere. 



The following list by no means includes all the birds which are upon the British List; it 

 is divided into two, the first portion including those species which have occurred so frequently 

 that even if we admit them as " vagrant," their wanderings suggest regularity of movement 

 towards the British area. The second portion includes a number of species which have been 

 observed on a few occasions only, and whose journey to our islands was probably caused by 

 influences affecting individuals rather than species. Many of these extraordinary occurrences 

 are probably due to the errors of youth, which almost invariably means subsequent death for 

 the individual. 



LIST I. 



Serin. Whitewinged-lark. Rock-thrush. Blyth's reedwarbler. 



Pine-grosbeak. Short-toed-lark. Whitespotted-blue- Aquatic-warbler. 2 



Blackheaded-bunting. Crested-lark. throat. Melodious-warbler. 



Meadow- bunting. Redthroated-pipit. 2 Alpine-accentor. Rosecoloured-starling. 



Rustic-bunting. WaUcreeper. Great-reedwarbler. Alpine-swift. 



1 See Coward, The Migration of Birdi, 1912, pp. 119-121. 



2 These, and probably others, may be classed as regular birds of passage. 



