Michigan Ornithological Club 79 



Errata : Cassinia reviewed on page 54 in the last issue, is the sixth rather 

 than the fourth number of the "Proceedings" of the D. V. O. C. Other vex- 

 ing errors crept into the last two numbers — some of which are the fault of the 

 editor, but most crept in after the proof had left the editor's hands. The full 

 "errata'' will be printed later. 



RECENT LITERATURE. 

 The Migration of Birds, With Special Reference to Nocturnal Flight. 



By H. A. Winkenwerder. Bull. Wis. Nat. Hist. Soc, Vol. 2 (N. S), 



No. 4, pp. 177-262, frontispiece and pis. i-viii. Milwaukee, Oct., 1902. 



The author divides his paper into four chapters, (I) A Historical Re- 

 view, (II) The Causes of Migration, (111) Migratory Routes, and (IV) The 

 Manner of Migration. The first two deal mainly with the writings of 

 previous authors, while only in chapters III and IV does he introduce to any 

 extent his own investigations. Chapter I covers some nine pages and gives 

 a fairly complete review of the principal writings on the subject of bird 

 migration, but also includes considerable discussion of the causes of migra- 

 tion, which are taken up more fully in the next chapter. After considering 

 the various theories of Wallace, Weismann, Merriam, Newton, Brooks, and 

 others, the author concludes that "Birds are set in migratory movement by 

 a complex combination of changes in temperature, humidity and living nature. 

 The cause for migration, however, is the failure of food in two widespread 

 areas — the north and the south — at opposite seasons of the year." While 

 recognizing the importance of the food supply as a "cause of migration," we 

 cannot help feeling that the author's statement is too sweeping, and that he 

 has not given sufficient weight to other factors, ncr taken into consideration 

 special cases. It is not probable that migration, even among birds, is a phe- 

 nomenon of homogeneous origin, to be explained in toto by any one set of 

 conditions, except, perhaps, in a most general way. Specific cases must have 

 each its own explanation, and in these explanations the varying influence of 

 heredity in the different species is a commonly neglected factor. 



Mr. Winkenwerder's original work consists of observations of migrat- 

 ing birds at night by the use of a telescope turned upon the moon ; this 

 furnishes a lighted field against which birds crossing the line of vision are 

 silhouetted. The same method has previously been used by Chapman and 

 others, but has been extended and systematized by Mr. Winkenwerder, who, 

 with the assistance of others, obtained nearly simultaneous observations at 

 several points in the Great Lake region. As regards Migratory Routes the 

 conclusions reached are not different from those generally held for the 

 majority of our summer-resident land birds, viz.: that there are several 

 great routes, or "trunk lines," so to speak, which the birds follow in coming 

 northward, principally determined by the major physiographic features, and 

 that from these the birds branch off gradually into routes of lesser and lesser 

 importance, until they finally become distributed to their various breeding 

 places. 



It is perhaps with regard to the Manner of Migration that the telescopic 

 method of observation offers us most of interest. Thus in regard to the 

 altitude attained in migration we are told that "The telescopic observations 

 show that there may be a zone of considerable depth, birds choosing variable 

 altitudes in which to perform their migrations, but by far the greater number 

 do not attain an altitude much over one-half mile from the earth's surface." 

 Another conclusion bears out what has already been surmised from field ob- 

 servations : "Birds do not fly to some desired resting place in one night and 



