KENNICOTTS WILLOW- WARBLER 335 



the inside of fine dry grass. There was neither feather nor hair used 

 in the construction. I did not see this bird further north than lat. 

 69°." 



J. H. Riley (1918) reports that Copley Amory, Jr.— 



took a nest and seven slightly incubated eggs on the Kolyma, directly opposite 

 Nijni Kolymsk, June 18, 1915. The nest was in swamp and willows on one side 

 of a "niggerhead," with water directly below the nest and a leaning dead willow 

 stick directly above. The nest outwardly is composed of rather coarse grass 

 with a few pieces of sphagnum moss, loosely woven; internally of finer grass and 

 lined with white ptarmigan feathers. The outer covering extends up over the 

 egg cavity, forming a roof. In fact, the nest has the appearance of two nests, 

 the outer one composed of dark-colored coarse grass and the inner of finer yellow- 

 ish grass. Outwardly the nest measures about 634 by 5 inches; the egg cavity 

 which is rounded 2 inches. The inner nest is placed in the front of the mass 

 that composes the outer nest. 



Eggs. — The Arctic willow-warbler lays a set of five to seven eggs; 

 probably six is the commonest number, but there are many sets of 

 seven. 



Mr. Riley (1918) describes the eggs taken by Mr. Amory as follows: 

 "The eggs are short, ovate in shape; white, rather evenly spotted with 

 larger and smaller spots of vinaceous russet in two tints; the spots 

 more numerous on the larger end. They measure as follows: 16.7 by 

 12.6, 16.4 by 12.5, 15.5 by 12.4, 16.4 by 12.5, 16.7 by 12.7, 16.5 by 

 12.6, 16.2 by 12.4 mm." 



Seebohm (1879) says that "the eggs are larger than those of our 

 Willow-Warbler's, pure white, and profusely spotted all over with 

 very small and very pale pink spots." 



Young. — Only one brood is reared. There can be little doubt that 

 only the female incubates, as in the case of its nearest relatives, though 

 this does not seem to have been positively proved. This conclusion 

 is supported by a statement of Robert Collett, who discovered Evers- 

 mann's warbler breeding in northern Norway and gave an excellent 

 account of it in the Proceedings of the Zoological Society of London 

 (1877). He mentions that a female he shot had large incubation 

 spots but makes no mention of these in males which he obtained. 



Plumages. — The plumages of Acanthopneuste b. borealis are de- 

 scribed by H. F. Witherby in the "Handbook of British Birds" (1938, 

 vol. 2) and by Ticehurst (1938, vol. 2). The nestling has not been 

 described. The juvenal plumage is much like the adult but less 

 greenish above, more inclined to grayish brown, and whiter below. 

 Ticehurst states that first autumn birds incline to be brighter and 

 greener than adults, less gray-green above and more tinged with 

 yellow on the underparts. "Usually too they can be recognized by 

 the unworn bar on the wings and the freshness of the flight and tail 



