September 26, 191 2] 



NATURE 



c|iiestion of "Weather Influences," and is an 

 admirable instance of careful scientific discussion. 

 So much nonsense has been written on this subject 

 that an authoritative statement is doubly welcome; 

 and not only has Mr. Eagle Clarke had the vast 

 data of the British Association Committee to draw 

 upon, but he has secured the valuable cooperation 

 of Dr. W. N. Shaw, Director of the Meteoro- 

 logical Office. 



To those who g-libly theorise on insufficient data 

 with regard to migrants' supposed preference for 

 ■'tail-winds," "beam-winds," and such like, we 

 commend what is said on page 173 : "The direc- 

 tion of the wind has in itself nothing to do with 

 the results described. The winds and the per- 

 formance, or non-performance, of the migratory 

 movements are the effects of a common cause — 

 namely, the particular type 

 of weather prevailing at the 

 time, which may be favour- 

 able or unfavourable for 

 the flight of birds to or from 

 our islands." Furthermore 

 we learn that similar condi- 

 tions — including wind direc- 

 tions — are favourable for a 

 movement both in spring and 

 in autumn, although the 

 direction of the movement is, 

 of course, exactly the oppo- 

 site at one season to what 

 it is at the other. Thus 

 " south-easterly weather " (a 

 large continental anticyclone 

 to the east of our shores but 

 extending to them, and 

 south-easterly winds in the 

 British area) favours migra- 

 tion across the North Sea in 

 either direction (according to 

 the season), but is unfavour- 

 able to intermigration be- 

 tween Britain and Iceland. 



The remainder of the 

 book may be divided into :. 

 two parts. Chapters ix.- Fic. 2.— iiann.in l 



xvi. deal in detail with 



the migrations of eight typical birds — swallow, 

 fieldfare, white-wagtail, song-thrush, skylark, lap- 

 wing, starling, and rook. Much of this valuable 

 work is already well known to those who have 

 followed the author's separate papers, but the 

 whole has been thoroughly revised. The second 

 volume and one chapter of the first deal with the 

 author's obser-\-ations at typical stations round 

 the British coasts — the Eddystone Lighthouse 

 (shown on a "bird-night" in a fine frontispiece 

 by Marian Eagle Clarke), the Kentish Knock 

 Lightship, Fair Isle (."the British Heligoland"), 

 St. Kilda, the Flannan Isles, Sule Skerry (west of 

 Orkney), Ushant (where the author was treated as 

 a spy !), and Alderney. An account is given of 

 the movements observed at each station, and what 

 is known in regard to each species of bird is terselv 

 summarised. 



It must be clearly understood that this admir- 

 able piece of work is not intended as a treatise 

 on bird-migration, summing up all that has been 

 done by various methods in different parts of the 

 world; it is an account of the author's personal 

 observations and inductions. This explains what 

 we cannot help regretting — the deliberate conden- 

 sation and reserve of the second chapter, which is 

 intended as a general introduction for the non- 

 expert, as the majority of zoologists, for instance, 

 must in this connection be called. But even for 

 such as these — the most appreciative of all readers 

 after ornithologists proper — the terseness is surely 

 overdone. Let us illustrate. In the few line's 

 devoted to migration in the southern hemi- 

 sphere, an important point has surely been ob- 

 scured in ignoring the great diflerence between 



XO. 2239, VOL. 90] 



inds: Eilean Mor from the ea^t. From "Studies in liird .Miijration. ' 



migration in the two hemispheres, that while 

 wtniy northern summer birds go far south of the 

 equator to "winter "in the southern summer, only 

 a few petrels and others from the south perform a 

 reverse journey of corresponding extent. Simi- 

 larly some mention of alternali\e views on the 

 origin of the migratory habit might well have 

 been given. Again, Mr. Clarke quotes with appar- 

 ent approval Mr. Chapman's opinion that the 

 recent experimental proof of the homing power 

 of the noddy and sooty terns dispels "the so- 

 called mystery " of how migrants find their way, 

 placing it on a par with "any other instinctive 

 functional activity." But this is an obvious iion 

 sequitur. Nor does it help matters to describe 

 the special sense of direction (in which Mr. Clarke 

 firmly believes) in Prof. Newton's phrase as "in- 

 herited but unconscious experience." .An interest- 



