2 Stubbs, The Use of Wind by Migrating Birds. 



have a curious effect on the fli,f:^ht of Gulls, compelling 

 them to move in a direction more or less directly heading 

 the wind. Thus a strong westerly wind causes great 

 numbers of Gulls to seek the estuaries and bays of our 

 east coast. On the other hand, strong westerly winds 

 will fill the estuaries and sea locks of the west coast with 

 these birds. The lee side of islands is also sought under 

 similar conditions of the wind," can be explained in another 

 way. A few writers, while not explicitl\' discarding this 

 "Head-wind Theory," have shown signs of leaning towards 

 the contrary opinion. A foot-note in Yarrell's " British 

 Hirds," (4th edit., vol. 3, p. 321) says: " It by no means 

 follows that the direction of the wind with which the birds 

 drop on the land is the same as that prevailing at a 

 greater elevation, and this should be taken into considera- 

 tion in estimating all records of the arrival of migrants." 

 Stevenson's "Birds of Norfolk" (vol. 2, p. 273) contains a 

 passage to much the same effect. It is strange that the 

 late Professor Newton altogether ignored the matter in 

 his comprehensive " Dictionary of Birds." 



Let us for the moment assume that Giitke and others 

 holding this " Head-wind Theory " are in the right. To 

 the observer on the coast, the velocity of the wind must 

 be at least about ten miles an hour. .At an altitude of 500 

 feet, which is a very low elevation for the path of a 

 migrating bird, the velocity would be perhaps double — say 

 for example 20 miles an hour. A Goldcrest, a familiar 

 migrant, desires to cross the North Sea to England, a 

 distance of from 250 to 350 mile.s. We may call it for 

 the present 300 miles, and allow the bird a velocity of 25 

 miles an hour. In a perfectly calm atmosphere the 

 journey would occupy 12 hours. When the so-called 

 favourable head-wind is blowing, that part of the earth's 

 atmosphere lying over Western Europe is moving east- 



