MIGRATION OF BIRDS 9 



breed and thus the bird becomes an irregular 

 summer resident or even, for the time, a per- 

 manent resident. 



6. Stragglers or Wanderers : birds whose occur 

 rence in our islands is more or less accidental, due 

 apparently to their having lost their way or to their 

 ordinary wandering habits having taken them far 

 from the normal range of their species. Some of 

 the rarer petrels and other oceanic birds certainly 

 pertain to this group, but our knowledge of the 

 migration routes of others is still so slender that it 

 is unwise to declare dogmatically that they are 

 lost. Some too of the so-called stragglers may 

 have been artificially or accidentally introduced ; 

 many ' records ' prove on investigation to be the 

 aimless wandering of escaped captive birds, whilst 

 others are known to have been aided in their journey 

 and carried out of their usual course when resting 

 on shipboard. 



When Mr Eagle Clarke was on the Kentish Knock 

 Lightship, off the mouth of the Thames, he found 

 that in autumn there were continuing practically 

 simultaneously the following streams of migration. 

 Immigration from the Continent to England from 

 east to west, and from south-east to north-west, 

 and passage along both lines ; emigration from 

 north to south-south-west, and from north-west to 

 south-east, with passage from north to south-south- 



