Winds on the Flight of Gulls and other Birds. 431 



snowstorm " in Heligoland, was pretty clearly shown to be 

 owing to high winds from the east. The 60 Little Gulls 

 {Larus minutus) recorded by the late Henry Stevenson in 

 1870 were drifted in before the violence of a north-east gale, 

 and so were the Pomatorhine Skuas [Stercorarius puma- 

 torhinus) in October 1879. Gales like these, and hurricanes 

 like that described by Mr. A. C. Chapman in 'The Naturalist ' 

 for February 1880, must be taken into account by those 

 who would study the movements of birds; but these phe- 

 nomena somewhat complicate the subject of migration, and, 

 by their irregularity^, make the problem more difficult to be 

 understood. 



It may be broadly said that the two great factors in avian 

 migration are the direction of the wind and food; and of 

 these the fonner is much the more potent, inasmuch as 

 wind continually retards migi'ation a good deal more than it 

 helps it. Few wall be found to deny that birds on migration 

 move fast or slow according to its velocity, and certainly 

 they move on or go backwards according to its direction. 

 Before long the wind drops, and the wished-for night of still- 

 ness comes, which, to the smaller feathered pilgrims espe- 

 cially, must be most welcome. Then, as Herr Gatke tells us 

 — in the results of a lifers observation now for the first 

 time made accessible to English readers — they rise high in 

 air, often probably to an immense height, and speed away 

 south at one hundred miles an hour (Swallows are said to 

 do 200), and in nine hours they are in Africa. 



This is evidently what happens to the multitudes of Scan- 

 dinavian migrants which come across the North Sea to the 

 British Isles in autumn. If they always continued flying 

 west they would find themselves in the Atlantic (and a recent 

 case was mentioned in * The Field ' newspaper in which that 

 actually happened to some Rooks), but they wait their oppor- 

 tunity and then they go south. 



2h 2 



