Recent Literature. 105 



ia^rntt ilittratitre, 



Henshaw's Report on Collections made in California, 

 Nevada, and Oregon in 1877- 78. — Mr. H. W. Henshaw's" Ornitho- 

 logical Report " * for the field seasons of 1877 and 1878 is much more than 

 a record of field observations for the seasons named, treating, as it does 

 most ably, though briefly, of the relationships of the members of several of 

 the most puzzling groups of North American birds. In addition to having 

 access to a large amount of material, much of •which the author collected 

 himself, he is able to bring to bear upon the questions at issue an intimate 

 knowledge of the birds in life, and of the varying conditions of environ- 

 ment which surround the forms treated. The routes followed during the 

 two years, the author informs us, " amounted practically to a continuous 

 line from Carson, near the western border of Nevada and a little south of 

 the Central Pacific Railroad, to The Dalles, on the Columbia River." 

 This gave opportunity for a comparative study of the birds of the several 

 regions traversed. The continuous chain formed by the Sierra Nevada of 

 California and the Cascade Mountains of Oregon " constitutes the first real 

 obstacle to the extension of animals and plants to the westward that is 

 encountered after the main chain of the Rocky Mountains, the 'backbone ' 

 of the continent, has been passed. So far, at least, as the extension of 

 birds is concerned," says Mr. Henshaw, " it appears to be an extremely 

 effectual one, and the rocky barrier thus constituted may be taken as lim- 

 iting with precision the Middle Faunal Province." Mr. Henshaw con- 

 siders, however, that this geographical barrier has less to do with the 

 absolute limitation of species than have the very diverse climatic condi- 

 tions that obtain on either side of it, coupled with the great change in 

 plant and insect life that these conditions entail. After a brief statement 

 of the nature and influence of these factors, the author proceeds to a formal 

 enumeration of the species and sub-species observed, some 1 85 in number, 

 with more or less extended notices of their habits and peculiarities of dis- 

 tribution. In the way of more technical matter, the author discusses at 

 some length the relationship of Cassin's Vireo to its near aflines of the 

 Rolitariua group, solUai'ius and pluinbeus. His conclusion is (p. 293) that 

 the Solitary Vireo, " like many other birds, appears to be divisible in 

 three distinct races, according as it inhabits the Eastern, the Middle, or 



* Oinitliologieal Report upon Collections made in Portions of California, 

 Nevada, and Oregon. By H. W. Henshaw. Annual Report of the U. S. 

 Geogr. Surveys west of the 100th Meridian for 1879. Appendi.x; L of the Re- 

 port of the Chief of Engineers, pp. 282 - 335. Feb., 1880. 



