946 U.S. NATIONAL MUSEUM BULLETIN 23 7 paet 2 



the pair records begin much later than the singing, despite the early 

 occurrence of pairs in adjacent territories. Hence pair formation 

 apparently may take place at any time from very early spring to 

 perhaps as late as the latter part of may. 



The male proclaims the territory he and his mate occupy by his 

 song in typical emberizine fashion. In my experience it nearly 

 always Ues on a moderately steep slope or across the two slopes of 

 a guUy or small canyon, more rarely astride a ridge. Harry L. Heaton 

 (1928) reports, "It is true the bird prefers a slope or hillside but * * * 

 I have found them nesting on comparatively level land some distance 

 from the hills and always quite removed from the abode of man. 

 The rim about an arroyo seems to appeal to them, probably because 

 it offers an easy disappearance into the depth below and reduces the 

 chances of enemy approach." 



The tendency for breeding pairs of rufous-crowns to be clumped, 

 discussed earlier for A. r. ruficeps, does not seem to have been men- 

 tioned in the literature for A. r. canescens. In the plots I studied in 

 the San Gabriel Mountains from 1950 to 1952 which were largely 

 composed of habitat suitable for the species, most rufous-crown 

 territories were relatively close to each other, leaving large unoccupied 

 areas near by. In some cases this may have been due to mutual 

 attraction to the more open ground along a road cut or head of an 

 eroding draw, but other grouped territories lacked such features. 

 Without a more thorough behavioral analysis, the question of a 

 possible social attraction seems unanswerable, even though the 

 evidence suggests it exists. 



Territory sizes were measured by planimeter from my mapped 

 records of the three plots in the San Gabriel Mountains in which 

 rufous-crowns occurred from 1950-52. In the 43.5-acre plot of 

 regrowth "chaparral" above Glendora at altitudes of 2,100 to 2,900 

 feet, 13 territories averaged 2.2 acres apiece, with extremes of 0.96 

 acres and 3.78 acres. In the 54.3-acre plot of coastal sage scrub in 

 the lower foothiUs, 14 territories ranged from 1.21 to 3.15 acres, with 

 an average of 1.9 acres. 



No description of the courtship in California races of Aimophila 

 ruficeps has been published. One display, however, seems to function 

 in much the same way in this species as does the similar one J. T. 

 Marshall (1960) described as a "squeal duet" or "pair reinforcement 

 duet" for the brown and Abert's towhees, or which was later described 

 (Marshall, 1964) as a "pair reunion duet." In the rufous-crowned 

 sparrow I saw the best display Apr. 3, 1952, in a canyon in the plot 

 above Glendora. From 9:26 to 9:35 a.m. one bird sang and gave its 

 typical dew, dew call from four locations on the west-facing slope 

 within 150 feet of a possible nest site, to which it went twice in this 



