70 



migratory hosts from different sources. The question of the 

 meteorological influences on an east-to-west autumnal move- 

 ment, vid the latter isle, therefore, need not be discussed here. 



In view of the fact that Herr Gatke attributes the presence 

 of many so-called far eastern species on Heligoland to the direct 

 influence exerted by the prevalence for any length of time of 

 light south-east winds, Mr. Eagle Clarke's remarks on winds in 

 general will be interesting. On pp. 25 and 26 he remarks : " The 

 importance attached to winds in connection with bird migration 

 has hitherto been much over-estimated by popular writers, and 

 their influence, such as it is, misunderstood. 



" The conclusions to be drawn from a careful study of the 

 subject are : (1) that the direction of the wind has no influence 

 whatever as an incentive to migration ; but that (2) its force is 

 certainly an important factor, inasmuch as it may make migra- 

 tion an impossibility, arrest to a greater or lesser degree its pro- 

 gress, or even blow birds out of their course. We have the 

 clearest proof, indeed, that birds do not migrate when the winds 

 are exceptionally high, though they sometimes pass into high 

 winds and gales en route, under the meteorological conditions 

 which have already been described and explained. Ordinary 

 winds — that is, winds not too strong — appear to be of small 

 concern to the birds, for they are recorded as migrating with 

 winds blowing from all quarters." 



The extracts presently quoted in this pamphlet will illustrate 

 the truth of the latter assertion. 



Mr. Eagle Clarke further remarks : "It is, however, a fact 

 that particular winds almost invariably prevail during the great 

 autumnal movements, and these have hitherto been considered 

 by some as the direct incentive to such migrations. Such 

 is not the case, and it may be at once stated that these sup- 

 posed favourable breezes are simply another direct result of the 

 pressure distribution favourable to the movement. . . The 

 winds prevailing and dependent upon the barometric conditions 

 are easterly, chiefly south-easterly, breezes. There is really no 

 reason why westerly (west, north-west, and south-west) winds, 

 not too strong of course, should not, other things being equal, be 

 in every way as suitable for migratory movements as those 



