CALIFORNIA THRASHER 405 



the ground, and by the reluctance of the sitting bird to be flushed, the 

 thrasher guards well the secret of its nesting site. 



Eggs. — [Author's note : The California thrasher lays two to four 

 eggs to a set, apparently oftener three than four and only rarely two. 

 These are mostly ovate, with variations toward elliptical-ovate or 

 short-ovate. They are only slightly glossy. The ground color is "Nile 

 blue," "pale Nile blue," or even paler blue. They are more or less 

 evenly covered with small spots, flecks, or fine dots of pale browns; 

 these are often very faint and sometimes much scattered; they are 

 very rarely conspicuously spotted, or even dotted with darker browns. 



The measurements of 50 eggs in the United States National Museum 

 average 30.1 by 21.2 millimeters; the eggs showing the four extremes 

 measure 34.0 by 21.3, 30.5 by 22.9, 26.4 by 20.8, and 30.9 by 19.8 milli- 

 meters.] 



Young. — According to Mrs. Irene G. Wheelock (1904), "both sexes 

 assist in the construction of the bulky nest, and both brood on the 

 eggs. In 14 days the naked pink young emerge from the shells and are 

 fed by regurgitation for 4 days, or until their eyes open." And from 

 the same source : "The young thrashers leave the nest when 12 to 14 

 days old, but are fed by the adults for some time after. I have found 

 the male caring for a fully fledged brood, while his mate was sitting 

 on a nestf ul of eggs ; and after this second series were hatched, he at 

 once began to feed them as faithfully as he had fed the first." 



In refutation of the theory that "a parent bird is moved to feed its 

 young only by that young bird's opening its mouth," Ernest I. Dyer 

 (1939) cited the behavior of this species, stating that "in the case of 

 every one of the 15 or 20 nests of the California Thrasher which [the 

 writer] has had under observation at his home, at 'reading distance,' 

 there have been innumerable instances of one or the other of the par- 

 ents' persistently trying to induce a totally unresponsive chick, by 

 duckings and bill-proddings, to open its mouth to receive food." 



The bills of the nestlings are proportionately shorter and much less 

 curved than those of the adults. After the young appear fully mature 

 in other respects, their bills are still noticeably short. Since the maxi- 

 mum sicklelike development of the bill is seen in comparatively few 

 individuals, it might be surmised that the growth of this member con- 

 tinues through a part, at least, of the adult life. 



Plumages. — [Author's note: According to Ridgway (1907), the 

 young are "essentially like adults but browner above, with larger wing- 

 coverts and tertials margined terminally with lighter cinnamon- 

 brownish, the rectrices more or less rusty brownish terminally ; chest 

 less grayish (more brownish), sometimes only slightly different from 

 general color of under parts." 



The postjuvenal molt of young birds occurs mainly in July, and the 



758066 — 18 27 



