May 19OI.] LAND BIRDS OF SANTA CRIV, COTNTY. 3 



FAUNAL POSITION OF SANTA CRUZ COI'NTV. 



The ti^reater ])art of vSanta Cruz County lies within the Pacific Coast 

 Transition l<'aunal Area.' This is a humitl tlivision of the Transition zone, 

 as defiueil l>v Dr. C. Hart Merriani. 'I'he belt extends from the Santa 

 Barbara Mountains north as a narrow stri]) next to the coast to the vicin- 

 ity of Cape Menchcino, where it merges into the boreal Northwest Coast 

 District. Tiiis Humid Transition^ belt continues north into the western 

 parts of Oret^on and Washington between the coast mountains and the 

 Cascade Rau'^e. In California the Humid Transition merges into the Arid 

 Transition on the east and occasionally into the Upper Sonoran. 



The Pacific Coast Transition Faunal An.'a is a region of heavy rain- 

 fall and of frequent fogs. In California the latter are especially prevalent 

 (luring the sunmier when there is little rain. As a result \-egetation is 

 luxuriant beyond any measure to be found elsewhere in California, ex- 

 cepting, of course, the northwest coast. 



With this humidity is correlat^;d a pL^culiarly etiuable climate. Through- 

 out the summer the mean temperature is low for the latitude, so that boreal 

 .species'^ cf animals and plants are enabled to push southward in low alti- 

 tudes. On the other hand the season of reproduction is much prolonged 

 on account of this singularly uniform climate. This brings the sum total 

 of summer heat rather high for the region, and many Austral or Warm 

 Temperate types are thus enabled to flourish.'' 



In the Santa Cruz mountains all these conditions exist. The region 

 is characterized by a rather heavy rainfall, particularly that area known 

 as the Big Basin. The climate is temperate, yet frosts occur in the moun- 

 tain canyons as late as the last of May. But on the other hand the total 

 amount of summer heat is high and thus it is that many forms found in 

 the Sonoran valley to the east and south are likewise familiar residents of 

 the Santa Cruz Mountains. ^ 



The Humid Transition portion of the Santa Cruz Mountains merges 

 into the Upper Sonoran on the outlying hills and valleys to the east and 

 southeast. This border land is usually one of great confusion in zone 

 boundaries, for plants characteristic of either zone will frequently be 

 found growing together in perfect amity. As a rule on these outlying 

 ridges, the upper and hotter slopes contain a totality of forms character- 

 istic of the Upper vSonoran zone, while the Transition is confined to the 

 deep canyons. Many mountains are covered with extensive areas of 

 chamiso { Adcnostoma fasciculatuni) which seem often to follow certain rock 

 formations. 5 Thus it is we find the Upper Sonoran zone ranging up high 

 on these peaks, for the chamiso, which is characteristic of this zone is able 

 to crowd out everything but chaparral plants and shrubs, and a large 

 quantity of heat is let in. The region affords an excellent opportunity to 



1 See I.ife Zones and Crop Zones of the United States by C. Hart Merriani. Bui. 10, I'. S. Dep't Agri. Div. 



Biol. Surv. 1898, p .27. 



2 This name will be used as a more convenient term for the Pacific Coast Tran.sition Faunal Area. 



3 Among the birds may be noted Anoithiiia hifmalis pacifica. Cyaiiocilta sit'llt'i i cai boiiacea. 



4 Such birds as Aphelocoma lalifot nica. Pipilo finciis crissalis, Carpoiiaciis pii>piirens laii/ornirus, I'heo 



gilviis s7vainsoni are examijles. 



5 For instance tho.se containing much lime sicm to be prclerred. 



