iSgi.] Recent Literature. 22 C 



lie, and of the effects of these climates upon the differentiation and dis- 

 tribution of the birds now found there. Mr. Chapman defines the moist 

 coast region as having its eastern boundary •■clearly determined by the 

 mountains of the Coast and Cascade Ranges," and as extending north- 

 westward to Kodiak Island, Alaska, and goes on to say : "In the present 

 condition of our knowledge the southern limits of this region can be deter- 

 minied with but slight approximation. The abrupt lines which restrict the 

 climatal conditions of the northern, eastern, and western boundaries are 

 wanting on the southern boundary, and we have here a more gradual 

 transition from the coast area of heavy rainfall southward into Southern 



California On the Californian coast the southern limit of the 



northwest coast fauna may probably be drawn in the vicinity of Cape Men- 

 docino, in Humboldt County, at about latitude 40*^ 30', or near the annual 

 isohyetal line of 38 in." In attempting to mark out a definite southern 

 boundary of the 'Northwest Coast Region,' Mr. Chapman has run against 

 the stumbling-block which lies in the path of everyone who tries to draw 

 hard and fast lines that do not exist in nature. Such a dividing line must 

 necessarily be purely arbitrary, for in reality there is no separation, one 

 thing shades imperceptibly into the other. The change from the forms 

 inhabiting the wet coast of British Columbia to their representatives that 

 occur farther south, is a gradual one and keeps even pace with the change 

 in climatic conditions. The farther south we go from Puget Sound the 

 less strongly marked is the rich and deep coloring that characterizes the 

 birds of that region. On the Oregon coast a difference ahead}' appears, 

 in the region of Cape Mendocino it has become greater, about San Fran- 

 cisco the divergence from the typical forms is still wider, yet even here 

 the affinity to the Northwest Coast races is very close. If, for the sake of 

 convenience, we are to lay down imaginary boundaries where Nature has 

 imposed no separation, it is probable that in the present case the line would 

 have to be drawn somewhere between San Francisco and Santa Barbara, 

 — not as far up the coast as Cape Mendocino. 



Mr. Chapman further discusses the influence of the moist coast climate 

 upon the differentiation of local races, and illustrates his remaiks by a 

 table of 31 characteristic coast forms contrasted with their representatives 

 in the interior. In bringing about this differentiation he says: "heavy 

 rainfall and humidity are primary factors, but the more immediate agents 

 are the dense vegetation and clouded skies of a moist region which afford 

 protection from the 'bleaching' rays of the sun." In other words it is 

 simply a question of exposure to light, and the relative moistui-e of the 

 atmosphere has nothing directly to do with the result. This is an as- 

 sumption which may well be questioned. 



Among other interesting things brought out by his study of these col- 

 lections Mr. Chapman finds that species, which in the arid regions of the 

 western United States are "differentiated from theii- Eastern allies, in sev- 

 eral instances appear in P>ritish Columbia in a plumage which more nearly, 

 if not exactly, resembles that of the Eastern form." Examples mentioned 

 are Chordeilcs virginianus^ Pooavtes gramineiis and Spizella socialis. It 



