VOl 'l9L5 XI1 ] Recent Literature. 511 



Position during Migration, Relation between Migration and Temperature, 

 Variations in Speed of Migration, The Unknown. The pamphlet is clearly- 

 written and places the subject before the public in such a way as to make 

 fascinating reading while it will undoubtedly interest a large number of 

 people in the study and recording of bird migration and so ultimately 

 serve to increase the data bearing on the subject. To the scientific man 

 this up to date treatment of one of the most interesting phenomena of 

 bird life will also prove of great interest, but he will look in vain for any 

 reference to other papers on the subject by the author or anyone else, 

 where he can follow up the matter and compare the various opinions 

 and theories that have been advanced. Such references may not be 

 required in Farmer's Bulletins or similar publications of the Department 

 of Agriculture, but in one of this sort, which appeals to scientists as well as 

 laymen, it seems that the universal custom in scientific publications should 

 have been adhered to and the value of the pamphlet thereby measurably 

 increased. 



While not for a moment questioning the accuracy of Prof. Cooke's 

 results in his studies of bird migration it seems pertinent in this connection 

 to call attention to an unfortunate tendency in most publications on this 

 subject in America, i. e. that of publishing ultimate results or theories 

 without presenting the detailed data upon which they are based. It may 

 be claimed that European publications on the subject represent a maximum 

 of detailed data and a minimum of conclusions, and this may be true, but 

 even so it is decidedly more in accord with the methods employed in other 

 lines of scientific work. 



In describing a new species or working out the geographic range of a 

 group of subspecies, pages are often devoted to the citation of detailed 

 data, where the results of the study is summed up in a few words. The 

 same method could be employed with advantage in works on bird migra- 

 tion, but too often we do not even know upon whose observations results 

 are based, or how many records or observers contributed to them. Further- 

 more migration tables or comparisons are not definite facts but are 

 averages and computations often involving the rejection of some of the 

 material, and the personal equation enters into this work to such an 

 extent that it seems absolutely essential that the most important details 

 involved in obtaining results should be presented. For instance, to take 

 an example from Prof. Cooke's paper, the isochronal migration line of 

 April 20 for the Black and White Warbler passes through Philadelphia, 

 yet in ' Cassinia,' 1912, p. 9, Prof. Cooke gives April 17 as the average 

 time of first arrival for Philadelphia while in 'Bird Lore,' 1905, p. 203, 

 April 27 is given (German town = Philadelphia). So also in 'Bird Lore,' 

 1905, p. 205, we find May 14 given as the average date of arrival 

 of the Black-poll Warbler for Englewood, N. J., but the isochronal line 

 for May 15 runs far north of this locality. Evidently these lines are not 

 based upon all the data at hand, some have been accepted and others 

 rejected, on good grounds no doubt, but the student who would judge of 



