NATURAL HISTORY STUDIES 



regularity and success. When weather conditions 

 are very unpropitious, there is often great mortality. 

 The streets of towns are sometimes strewn with 

 thousands of birds that have gone astray and have 

 perished in the cold. As many as five hundred 

 nightingales have been gathered in a single day from 

 one small town. But, on the whole, the striking 

 fact is not the number of failures but the large 

 proportion of successes. This is the more striking 

 when we think of the difficulties of a long migration 

 journey. What we are made to feel is that 

 migrating is an old-established business ; it has 

 been going for so many hundreds of thousands of 

 years that it now works very smoothly. A thrush 

 born in the North of Scotland was found at the end 

 of its first summer near Lisbon a long journey for 

 an inexperienced traveller who is hardly counted as 

 a migrant at all. And there are many similar 

 instances. 



The feature of regularity is also seen in the 

 remarkable punctuality of arrival and departure 

 which is often exhibited, except, indeed, when the 

 weather conditions are unusual. Fog and head-winds 

 may delay arrival ; a summer that has favoured the 

 increase of insects may induce birds to postpone 

 their departure ; but, on the whole, there is a 

 remarkable regularity in the comings and goings. 



Still more remarkable is the fact that in some 

 cases there is conclusive proof of a bird's return to 

 its birthplace. A swallow marked as a youngster 

 with an aluminium ring has been known to return 

 the following year from its winter quarters, not 



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