GEOGRAPHICAL ASPECTS 101 



summer, also traverse similar tracts of country when 

 passing to and fro — among them are the Golden Plover, 

 Curlew, etc. 



The VVhimbrel {Numenms phcropus) is another 

 species which passes overland in spring and autumn, 

 though it apparently does not follow very definite inland 

 routes — a circumstance which is no doubt accounted for 

 by the fact that it seldom alights to feed. It is 

 generally observed passing north or south, accord- 

 ing to the season, at a considerable elevation, attention 

 being drawn to it by the well-known and peculiar call- 

 note which is continually uttered. In my experience, 

 gained in central Yorkshire, these birds pass over during 

 the daytime, and usually singly or in pairs. 



Racial Forms of Migratory Birds.^ — In connec- 

 tion with the geographical aspect of bird migration, it is 

 of importance to allude to the racial forms to be found 

 among a number of the species which occur as visitors 

 to our islands and their shores. Much attention has, 

 fortunately, been paid to the study of these geo- 

 graphical forms during recent years, especially by Dr 

 Hartert, who has made many of them known to us, and 

 is treating of them in his excellent work. Die Vogel der 

 paliiarktischen Fauna. 



A knowledge of these geographical races is of the 

 utmost value to those interested in bird-migration, for it 

 enables the student in a number of cases to determine 

 whence certain migrants set out on their journeys to reach 

 our shores — a gain the importance of which it is impos- 

 sible to over-estimate. A number of these racial forms 

 regularly appear in our islands, either as seasonal visitors 

 or as occasional guests. Among these are Continental 



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