28 THE ORNITHOLOGIST. 



east coast of England generally. The direction taken by 

 Rooks and other birds would be changed if the prevailing 

 winds blew from any other quarter than west, for they like 

 flying against it, account for it how we may, though it is not 

 to be denied that there are now and then exceptions. But a 

 cause for such may be guessed at, if sought for. 



On the other hand, a gale of even moderate strength, from 

 whatever quarter, has a very different effect, bearing all the 

 sea-birds and land- birds alike before it if strong, and for the 

 smaller land-birds a very slight puff will suffice. The memor- 

 able flight of Blue-throats (Cyanecula suecica) to the coast 

 of Norfolk in September, 1884, was considered by those on the 

 spot to be immediately after an east wind increasing in force 

 and very gusty, which the Blue-throats must have flown with, 

 and not against. The vast incursion of Gold-crests (Begulus 

 cristatus) in the autumn of 1882, which extended far beyond 

 the limits of Norfolk, and was "like a snowstorm" in the 

 island of Heligoland, was pretty clearly shown to be owing to 

 high winds from the east. The sixty 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 Pomatorhme Skuas (Stercorarius pomatorhi?ius) in 

 October, 1879. Gales like these, and hurricanes like that 

 described by Mr. A. C. Chapman in "The Naturalist" for 

 February, 1886, must be taken into account by those who 

 would study the movements of birds ; but these phenomena 

 somewhat complicate the subject of migration by their 

 irregularities. 



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 former is much the more potent, inasmuch as wind con- 

 tinually retards migration a good deal more than it helps it. 

 Few will 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 stillness comes, which, 

 to the smaller feathered pilgrims especially, must be most 

 welcome. Then, as Herr Gatke tells us — in the results of a 

 life's observation, now for the first time made accessible to 



