liUITISH ISLES AM) TMEIR MIGRATORY BIRDS 39 



but on the part of very much smaller numbers both ot 

 species and of individuals. 



Casual Visitors. — Another class of bird-visitors to 

 our islands now claims attention — namely, the Irregular 

 or Casual visitors. Each year a number of Continental, 

 Asiatic, African, and American species appear on our 

 shores as stragglers, many of them after having per- 

 formed remarkable peregrinations. Though rich in 

 the number of forms, these waifs are comparatively 

 poor in individuals, and mostly belong to species which 

 annually perform extensive migratory journeys. In the 

 great majority of cases they arrive in the autumn and are 

 juveniles ; and their appearance among us is, probably, in 

 most instances due to the errors or indiscretions of youth : 

 they have failed to follow the right course leading to the 

 usual winter retreats resorted to by their race. They 

 inherited the migratory impulse in its undiminished 

 force, but the unconscious experience has for some 

 unknown reason been denied them, and they mostly 

 share the fate which nature rigorously imposes on 

 the ''unfit." In some cases, possibly often, they 

 may have been overtaken by adverse weather when 

 making for their accustomed seasonal haunts, and 

 thus have been driven out of their course, to be 

 stranded in localities where they would not otherwise 

 have occurred. 



In spring much smaller numbers of these waifs appear 

 on our shores. Their appearance at that season far 

 beyond the bounds of their usual summer quarters may, in 

 some instances, be accounted for, perhaps, by an excess of 

 zeal having led them to overshoot, as it were, the ordinary 

 limits of their range ; while in others, strong winds may, as 

 in the case of some of the autumn stragglers, have carried 



