SCOTT'S RUFOUS-CROWNED SPARROW 927 



Eggs. — The eggs, usually three in number in Arizona, vary (for the 

 species as a whole) from two to five. They are ovate, slightly glossy, 

 very pale bluish-white, and unmarked. The measurements of 71 eggs 

 average 20.0 by 15.6 millimeters; the eggs showing the four extremes 

 measure 22.8 by 16.8, 17.9 by 15.7, and 19.1 by U.2 millimeters. 



Incubation. — The rufous-crowned sparrow is a very close sitter. 

 The incubating bird usually does not fly until nearly stepped on, and 

 thus betrays the whereabouts of the nest. No detailed studies of 

 incubation or care of the young have been made. 



Plumages. — The ju venal plumage is rather variable. Usually it is 

 heavily streaked with dusky on the chest, sides, crown, and back; 

 these streaks are sometimes so faint that they are hardly noticeable 

 until in the hand. The streaks are never conspicuous on the dark 

 brown background of the upperparts. This background color varies 

 considerably in hue and depth, but is never pale and sandy as in A. 

 carpalis. The variation is especially conspicuous on the upper tail 

 coverts. Similarly, the whiskermark is often obscure, and the deep 

 grayish median crown stripe is hardly visible except in the most 

 dusky-crowned individuals. Below the pale superciliary is a hint of an 

 eyeline of the same color as the dark crown; this becomes a rufous 

 eye stripe, as in adidts, about as soon as the bird is fuUy grown. 

 Before then the white eye ring is about the only conspicuous head 

 marking. Very young birds have narrow, dull buffy wing bars. 



The first prebasic or postjuvenal molt varies somewhat, probably 

 according to when the bird w^as hatched. In Arizona and Sonora 

 it rarely involves the tail or the primary coverts, and perhaps never 

 the inner ones. The body, tertials, and lesser and secondary coverts 

 are regularly molted; the primaries and alula are molted less fre- 

 quently. This molting time varies but molting is probably completed 

 in most cases by November 1 , at which stage young and old look alike . 



I have detected no prenuptial or prealternate molt. Adults molt 

 late — in Arizona the molt is completed about early November. To 

 the south in Oaxaca, a female A. r. av^tralis was in heavy molt, but 

 stUl not far advanced into it, on Nov. 23, 1958. 



It should be mentioned that young males I took in Arizona Apr. 20 

 and 27, 1958 stdl had the occipital part of the skull partly or wholly 

 un ossified; yet they were in breeding condition. Under favorable 

 weather conditions, therefore, they may breed when less than a year 

 old. Also the rate of ossification of the skull may sometimes lag, 

 being far slower than in most small songbirds; for these males could 

 hardly be less than lYi months old; one still had frontal windows as 

 well in the skull. Further, the apparently breeding female from 

 Jahsco, May 15, 1959, still shows indications of windows laterally in 

 the occipital region. 



646-737—68 — pt. 2 22 



