178 STUDIES IN BIRD-MIGRATION 



are recorded — the birds arrive in small numbers and 

 come little under notice. 



There are other types of weather which, in like 

 manner, favour particular migratory movements, but are 

 unfavourable for others. Thus the North-Easterly Type 

 is the most favourable for migration between Iceland 

 and the British Isles, but is not suited for movements 

 between our shores and those of countries lying to the 

 south and south-east of them (see Plate VII.). The 

 South- Westerly Type is conducive to intermigration 

 between England and Central and Southern Europe, 

 but presents barriers to passages between our Isles and 

 Northern Europe and Iceland (see Plate VIII.). 



Winds. — The importance of winds in connection with 

 bird-migration has been much over-estimated, and their 

 bearing upon the phenomenon, such as it is, greatly 

 misunderstood. Their direction, apart from the weather 

 conditions to which they are due, has no influence 

 whatever on the movements. Thus, if a migrant were 

 crossing the North Sea from Norway to Britain, one 

 fails to see why a north-west wind should not be as 

 suitable for the passage as a south-east, for both would 

 be beam-winds, and yet during the prevalence of the 

 former, such migration is practically at a standstill, and 

 during the latter at its climax. 



High winds, from any quarter, are naturally 

 unfavourable, inasmuch as their very force may render 

 migration impossible or disastrous, or force the birds 

 out of their course when they encounter them. Strong- 

 flying species, such as Swans and Geese, do, indeed, 

 migrate under stress of weather that would be fatal to 

 most of the smaller species, and appear in our islands 

 during very unsettled periods. It is extraordinary. 



