BIRDS OF THE PACIFIC DISTRICT. 6 



therefore, unsatisfactory. It will, however, be preserved 

 for future use. All persons are credited with the data 

 which they contributed to the report, which has been 

 simply a labor of love from beginning to end. 



In California the spring migrating land birds almost 

 invariably come gradually and almost imperceptibly, 

 probably many arriving in the night or early morning; 

 and I have never seen, on the Pacific Coast, what might 

 properly be termed a "bird wave," except upon one oc- 

 casion, and that was in the spring of 1866, before I 

 began to keep a record of bird movements. Mr, F. 

 Stephens noticed a "bird wave " at Campo, San Diego 

 County, the last of April, 1877 (Bull, Nutt. Orn. Club, 

 July, 1883, p. 188). Except these, I know of no other 

 occurrences of this kind on this Coast, of course ex- 

 cluding the occasional movements of large bodies of 

 geese and ducks. It is very difficult, therefore, to as- 

 certain the lines of flight, but we may conclude that 

 many summer residents of California and northward 

 bear well to the east in seeking their winter quarters in 

 the tropics, as at least a dozen species which breed in 

 California have not been observed much south of San 

 Diego at any time, among these being such conspicuous 

 species as Bullock's oriole and the Arkansas flycatcher, 

 which, in common with the other species, occur far 

 south on the mainland in Mexico in winter. Then 

 there are summer residents of Washington, British 

 Columbia and Alaska which have never been collected 

 in California, though they spend the winter in the 

 tropics. The high Sierra Nevada and Cascade ranges 

 would seem to be an impassible barrier to the migrants, 

 and they undoubtedly have great influence in determin- 

 ing lines of flight — but not nearly as much as would 

 naturally be supposed, as a number of species which 

 winter in California migrate vertically and spend the 

 summer on the east slope. 



