242 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM:. 



ilependent ou the alteruatioJD! of wet and dry seasons, which prevails in 

 less degree along the whole coast noithward. 



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 farther north, but of which uo records exist 

 for this coast, l^orth 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 Mojave, Colorado Valley, though the winter is 

 colder than at San Diego, it is much drier, the chmate, like 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 farther north) Avould account for. Many si^ecies 

 are also found wintering there which do not remain along the raiu}^ 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 forther 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. Ridg- 

 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 ISTe- 

 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 

 have reached 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 near the California coast. 



The moderately dry parts of California, where, south of latitu<le 

 38°, 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 



