312 BREWSTER'S WARBLER. 



of the Golden-winged Warbler and the Blue-winged Warbler, — a Mendelian 

 so-called dominant hybrid, as Mr. J. T. Nichols suggested in The Auk, Jan., 

 1908, 25, p. 86. 



Since my memoh' was published, Golden-winged Warblers and Brewster's 

 Warblers have bred every year in the Lexington swamp. In 1911 Dr. W. M. 

 Tyler and I devoted a good deal of time to them, but without any very definite 

 results. There were during that season at least one male Brewster's Warbler, 

 and one female Brewster's Warbler, together with approximately three male 

 and three female Golden-wings; both Golden-wings and Brewster's Warblers 

 were reared by these birds, but unfortunately we failed that summer to discover 

 how the old birds were paired off. 



In the summer of 1912 I lived so far away from Lexington that I was unable 

 to pursue the study of this interesting little colony of birds to any advantage. 

 However, in a visit to the place on the 27th of May, I found a male Brewster's 

 Warbler in song,' and on the 4th of July Dr. Tyler saw a male Golden-wing 

 and a female Brewster's Warbler feeding a brood of young birds, one at least 

 of which was a young Brewster's Warbler, while in another part of the swamp 

 he met with a female Golden-wing with a brood containing Golden-wings and 

 Brewster's Warblers assuming their first winter plumage. 



In the spring of 1913 I resiuned my residence in Lexington and, in associa- 

 tion with Dr. Tyler, continued the study of the Warbler colony. The Golden- 

 winged Warbler arrived this year on the 6th of May, a rather early date for this 

 species.- The population of the swamp, so far as the birds were concerned in 

 whom we were especially interested, consisted of a male Golden-wing, a female 

 Golden-wing, a male Brewster's Warbler, and a female Blue-winged Warbler. 

 The male Golden-wing was mated with the female Blue-wing, the male Brews- 

 ter's Warbler with the female Golden-wing. No nests were found, and the 

 manner in which the birds were paired off together was not determined till the 

 young birds had left the nests; in fact neither of the females was seen until then, 

 about the middle of June. All of the old birds were perfectly typical in plumage, 

 the male leucohronchialis being one of the pure-plumaged specimens that show 

 not the faintest trace of yellow on the under parts. Here at last we had the 

 combination we had so ardently wished for, l)ut hardly hoped to find, — the 

 Golden-wing mated with the Blue-wing, — and we now followed with keen inter- 



' I fake this opijortunily to reconl another male Brewster's Warbler which I saw in full song near 

 Walden Pond, Concord, Mass., on May 19, 1912. 



2 The average date of arrival of this bird in the neighborhood of Boston, based on my records for 

 24 years, is May 11. The earliest date within that period is May 3, 1905, the latest May 15, 1908. 



