NORTHERN OLIVE WARBLER 157 



usually well scattered over the entire surface, but tend to become 

 heavier at the large end. The measurements of 28 eggs average 17.1 

 by 12.8 millimeters; the eggs showing the four extremes measure 

 19.0 by 16.0, 16.0 by 12.2, and 18.1 by 12.0 millimeters (Harris). 



Young. — Information is lacking on incubation and care of the 

 young. 



Plumages. — The plumages and molts of the olive warbler are as 

 distinctive as its nest and eggs. The sexes are not quite alike in 

 Juvenal plumage. Ridgway (1902) describes the young male as 

 "pileum, hindneck, back, scapulars, rump, and upper tail-coverts plain 

 dull olive or brownish olive ; supra-auricular region and sides of neck 

 dull yellowish buify, the latter tinged with olive; chin, throat, and 

 chest dull yellowish buffy ; otherwise like adult female." And of the 

 young female, "similar to the young male but paler and grayer above ; 

 supra-auricular and post-auricular regions pale brownish buffy ; chin, 

 throat, and chest still paler buffy, the chin and upper throat dull 

 buffy whitish." The white tips of the greater wing coverts are tinged 

 with yellowish. 



I have not been able to trace the postjuvenal molt in the series I 

 have examined but it apparently occurs in July and produces very 

 little change, young birds of both sexes in their first winter plumage 

 closely resembling the adult female at that season, though the crown 

 and nape are grayer and the throat and breast are paler. I can find 

 no evidence of a prenuptial molt. Young males evidently breed in this 

 plumage and do not acquire the fully adult plumage until their sec- 

 ond fall, or perhaps later. In Brewster's series, collected in March, 

 three males are in this condition, of which he (1882) says that "two 

 of them, although in unworn dress, are absolutely undistinguishable 

 from adults of the opposite sex; the third (No. 77), however, has the 

 throat appreciably tinged with the brownish-saffron of the adult 

 male." This last may be a bird that is one year older, for Ridgway 

 (1902) describes the "second year" male as "identical in coloration 

 with the adult female." Judging from the series that I have ex- 

 amined, including all of Brewster's birds, I am inclined to think that 

 the adult winter plumage is acquired at the first postnuptial molt, 

 or when the bird is a little over one year old. 



There can be no doubt, however, that young males breed in this 

 immature plumage, for Price ( 1895 ) secured a pair that were feeding 

 a brood of young, and the "male was not in fully adult plumage and 

 was very similar in coloration to the female." Swarth (1904) writes : 

 "The male bird breeds in the immature plumage, for on June 21, 1902, 

 I assisted O. W. Howard in securing a nest, containing four eggs, 

 the parents of which were indistinguishable in color and markings. 

 * * * I was surprised at the large proportion of birds in this im- 



