Vol. XXII 

 '9°S 



Clark, Afigratiotis of Shore Birds. \ -? c 



As long ago as 1848, Sir Robert H. Schomburgk made the 

 interesting observation (Hist. Barbados, p. 681) that these plover, 

 in common with other shore birds, when flying over the island of 

 Barbados (the most easterly of the West Indies) take a course 

 from northwest to southeast, at right angles to the direction of 

 the wind (the northeast trade). Col. H. W. Feilden, in writing 

 of the birds of Barbados (Ibis, 1889, p. 490; West Indian Bulle- 

 tin, III [1902], p. 343), also notes this fact adding that "it 

 appears to be a well established observation that birds prefer 

 migrating with a ' beam ' wind." When in Barbados in September, 

 1 90 1, I was told by several sportsmen that the shore birds were 

 always seen to pass the island flying from northwest to southeast, 

 and I observed the fact myself in the migration seasons of 1903 

 and 1904. 



Thus it appears that within the trade-wind belt, at least, these 

 birds always direct their flight in a definite relation to the direction 

 of the wind. With us, living in the north temperate zone, the 

 winds are so irregular and variable that we can hardly form any 

 accurate idea of the regularity of the winds within the tropics, 

 and to a lesser extent, over the sea in general, unless we have had 

 more or less experience with them. 



Acting upon the supposition that the invariable relation of the 

 flight of the Golden Plover to the direction of the wind when in 

 the West Indies might be in reality a key to the course taken by 

 them during the major part, if not the entire extent of their flight, 

 I have mapped out a theoretical course which the birds would 

 follow, provided they depended on the direction of the wind as a 

 guide, and flew always at right angles to it. 



There is one important point to be borne in mind in connection 

 with this, and that is that a bird flying directly across a wind will be 

 carried to leeward out of the course it appears to be taking just as 

 many miles every hour as the force of the wind is miles per hour. 

 I may illustrate what I mean by a parallel case. If a man were to 

 row a boat at the rate of four miles an hour across a stream with 

 a current of two miles an hour, which (let us assume) it takes him 

 an hour to cross, if he rows always with the axis of the boat at 

 right angles to the force of the current, he will reach the other 

 bank at a point as far down stream from a position exactly 



