ASHY RUFOUS-CROWNED SPARROW 945 



Studies of the breedinp; birds of six plots farthei east id the San 

 Gabriels included mapping territorial activities and coni[)iiling popu- 

 lations on both a space and time basis in units of ''full season terri- 

 tories," each unit equal to a territory wholly within the plot occupied 

 throughout the period of mapping, usually about 10 weeks (Cogswell, 

 MS.). The plot in this series with the sparsest shrubs was studied 

 3 to 5 years after a fire, when about 44 percent of the ground was 

 covered by shrub canopies and the regrowing chamise, scrub oak, 

 manzanita, and Ceanofhus were still far overshadowed by vigorous 

 black sage (Salvia meUifera), deerweed (Lotus scopariiis), and several 

 other subshi"ubs. On this 43-acre plot near Glendora, the rufous- 

 crowned sparrow populations had 2.5, 3.4, and 5.8 "full season terri- 

 tories" per 100 acres in 1950. 1951, and 1952 respectively. 



In the one plot of the six that lay below the main chaparral belt, on 

 a low foothill near San Dimas where the vegetation was typical 

 coastal sage scrub with only a few patches of chamise and of poison 

 oak, about 55 percent of the ground was covered by shrub canopies, 

 mostly California sagebrush, California buckwheat, white sage, and 

 a prickly pear cactus (Opuntia occidentalis) , with scattered taller Yucca 

 whipplei and the laxly branched laurel sumac (Rhus laurina). Here 

 the populations of rufous-crowned sparrows in the same 3 years had 

 6.9, 5.7, and 3.9 territories per 100 acres, the decline being due in the 

 last year to the disappearance of several territory holders dming the 

 spring. 



In view of the roughly similar population densities of rufous-crowned 

 sparrows in these two plots despite the strong differences in slirub 

 species composition and other differences in the herb cover, the factors 

 favoring occupancy of "scrub" types of vegetation in this area are not 

 so much dependent upon any particular species of shrubs as on their 

 general low form and interspersion with lower, non-woody plants. 

 This may even apply to the species' supposed preference for Artemisia 

 caiijornica cited by Joseph Grinnell and Alden Holmes Miller (1944) 

 and other authors, for that shrub was almost entirely absent from the 

 recently burned area near Glendora. 



Spring, territorj/ and courtship. — In the foothUls of the San Gabriel 

 Mountains I have noted a few rufous-crowned sparrows in obvious 

 pairs as early as February 1. Indeed some may remain in pairs 

 through the winter, as advertising song by many of the males does not 

 begin until mid-March or later, a considerable length of time after 

 many pairs are found foraging together and keeping in touch by call 

 notes. Of 45 temtories in 5 of the study plots I examined from 1946 

 through 1952, in 10 no rufous-crowned sparrow other than the singing 

 male was detected; most of these birds were presumably unmated, 

 though some females were probably missed. In quite a number more, 



