98 THE MIGRATIONS OF BIRDS 



Gatke at Heligoland has recorded incredible num- 

 bers of the European jay in passage for three days in 

 October, 1882, while in subsequent years only one 

 individual was seen. 



It is probably true that many vagrant individuals 

 are carried so far beyond the usual range that they 

 fail to make any attempt to return, and many others 

 perish through unfamiliarity with the dangers of the 

 new environment into which they have come. It is 

 probable from the records available that most of the 

 sand-grouse in the invasion mentioned in 1863 and 

 1864 perished, since everywhere the strange birds 

 were hunted and killed. 



Wastage of individuals among migrants is exten- 

 sive, and affects vagrants as well as those regular in 

 travel. It would seem to operate with greater sever- 

 ity among those of irregular movement, as such have 

 established no regular annual margin of safety. We 

 may look then upon these periods of vagrancy to cut 

 down the number of individuals among the species 

 concerned. These erratic spreads have probably 

 served to extend the -range of some species, and may 

 still do so, though since the rise of man this has be- 

 come difficult except in the case of inconspicuous 

 forms. 



Flights of snow buntings, longspurs, pine siskins, 

 redpolls, and many others that penetrate irregularly 

 to the southward during severe winters may hardly 



