242 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



depeudent ou the alternatiou of wet and dry seasons, wliicb prevails in 

 less degree along the whole coast northward. 



It is indeed the excess of rain until quite late in spring, which ap- 

 pears to prevent the earlier laying of eggs by some species that begin 

 to lay in the east earlier than on this slope. This is noticeable among 

 Hawks and Owls, and may also be expected with the Crossbills, 'Wax- 

 wings, and others breeding ftirther north, but of which no records exist 

 for this coast. Xorth of latitude 00^, however, where Professor Dall found 

 so many eastern species mixed with the western, the division into wet 

 and dry seasons is not marked, which may account for the breeding 

 there of those eastern birds not found south of that latitude on this 

 coast. 



In California we find the influence of the rains causing considerable 

 difference in dates of laying in various localities, where they end sooner 

 or later. Thus at Fort Moja\e, Colorado Yalley. though the winter is 

 colder than at San Diego, it is much drier, the climate, lilvC that of Ari- 

 zona, being wet in summer. I therefore found the same species laying 

 much earlier at Fort Mojave, though the arrival of migratory birds 

 was generally later, more so than the difference of latitude (one hun- 

 dred and forty miles fiirther north) would account for. jMany species 

 are also found wintering there which do not remain along the rainy coast 

 at that season. 



At Haywood, on the east side of San Francisco Bay, I also found 

 many species laying earlier and more abundantly than at Santa Cruz on 

 the coast, forty-eight miles farther south, but more rainy. This last 

 place is itself much more favorable to most species than the foggy cool 

 promontory of Monterey, twenty-five miles southward. 



Of the influence of climate in localities still farther inland I cannot 

 state much from personal observation north of Fort Mojave, but have 

 quoted some interesting dates for comparison, reported by Mr. Eidg- 

 way at Sacramento, though of less value in this connection than if he 

 had been there earlier and later in the season. 



On account of the great elevation and very different climate of Ne- 

 vada and Utah, his observations there are of little value for comparison 

 with Western California, though in some degree comparable with Fort 

 Mojave. 



The period at which rains cease being quite different in different 

 years, we also find considerable variation in the arrival of some birds 

 as well as in dates of laying at any locality selected. In some years the 

 migrants seem to take a much more inland route northward than in 

 others, not appearing along the coast until long after their comrades 

 * hiive rcached even to Alaska. Thus Mr. Dall records the arrival and 

 laying of some species along the Yukon at about the same times they are 

 recorded netir the California coast. 



The moderately dry parfs of California, where, south of latitude 

 380, trees are limited chiefly to the northeast slopes of hills and the 

 banks of streams, we find to be the favorite breeding grounds of most 



