Recent Literature. 
105 
§£Uf«rt EtUrature. 
Henshaw’s Report on Collections made in California, 
Nevada, and Oregon in 1877 - 78. — Mr. H. W. Henghaw’s “ Ornitho- 
logical Report ” * for the field seasons of 1 8 7 7 and 1 8 78 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 185 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 Yireo to its near affines of the 
solitarius group, solitarius and plumbeus. His conclusion is (p. 293) that 
the Solitary Yireo, “ like many other birds, appears to be divisible in 
three distinct races, according as it inhabits the Eastern, the Middle, or 
* Ornithological 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. Appendix L of the Re- 
port of the Chief of Engineers, pp. 282 - 335. Feb., 1880. 
