Brewster's Warbler (Vermioora leucobronchialls) in Lexington, 



Mass. — In ' The Auk ' for October, 1907, I recorded a Brewster's Warbler 

 found during the summer of that year in a swamp in Lexington, Mass. 

 In the decade that has since elapsed, this bird has been found estabUshed 

 in the same swamp every summer except that of 1909, when no search 

 was made for it. In 1910 and 1913, Dr. W. M. Tyler and I made a careful 

 study of this hybrid and its relations with the Golden-winged Warbler 

 (7. chrysoptera) and the Blue-winged Warbler (7. pinus). The results 

 of om- observations were published by me in the Memoirs of the Museum 

 of Comparative Zoology, Vol. XL, Nos. 2 and 6, January 1911 and August, 

 1913. The persistence of this hybrid form in the same locality through 

 so many consecutive years is in itself well worthy of record; I wish, too, 

 to summarize the knowledge acquired relative to the matings of these 

 birds and the duration of the nestling period. 



In the season of 1910 there were two pairs of which the males were 

 Golden-wings, the females Brewster's; one pair of Golden-wings; and one 

 unmated male Brewster's. The issue of one of the heterogeneous pairs, 

 Golden-wing and Brewster's, were all Brewster's Warblers, of the other, 

 a mixed brood of Golden-wing and Brewster's. The pair of Golden- 

 wings produced Golden-wings only. 



In 1912 a male Golden-wing mated with a female Brewster's. 



In 1913 a male Golden-wing mated with a female Blue-wing, a male 

 Brewster's with a female Golden-wing. The progeny of the first pair 

 were all Brewster's, of the second pair one Golden-wing plus several 

 Brewster's. 



In 1914 a male Brewster's mated with a female Golden-wing; their nest 

 was not discovered till June 16, the day the young left it. 



In 1917 a male Brewster's mated with a female Golden-wing. Here are 

 six cases of the mating of Brewster's Warbler, each time with a Golden- 

 wing, and one case of a Blue-wing mated with a Golden-wing. Observe 

 that all previously published accounts of the pairing of Brewster's Warbler 

 have been records of the union of this form with either a Golden-wing or 

 a Blue-wing (see my paper in Mem. Mus. Comp. ZooL, Vol. XL, No 2 

 p. 71). 



It is worthy of note that the numerous Golden-winged and Brewster's 

 Warblers seen in this locality during these years have without exception 

 exhibited an absolute purity of plumage in spite of the constant crossing 

 of the two forms. In other words, no plumage intermediate between the 

 Golden-wing and Brewster's has cropped out. 



Duration of the nestling period: in 1897 the five eggs m a nest belonging 

 to a pair of Golden-wmged Warblers (Arlington, Mass.) hatched June 8, 

 the young left the nest June 15. In 1910 the five eggs of a Brewster's 

 Warbler mated with a male Golden-wing hatched June 8, the young left 

 the nest June 17. In 1917, the five eggs of a Golden-wing mated with a 

 male Brewster's Warbler hatched June 21, the young left the nest June 

 29-30. The life of the young birds in the' nest therefore covers from seven 

 to ten days. 



The spring of 1917 was without precedent in its backwardness. V. 

 chrysoptera did not arrive until May 19. This is latest date for the arrival 

 of this bird in my records of twenty-eight years, the average time of 

 arrival being May 11-12, the earliest. May 3 (1905). This wUl account 

 for the phenomenally late breeding of the 1917 birds given above. 



Several other locahties in the town of Lexington are the home of Golden- 

 winged Warblers, but none of them have ever yielded a Brewster's Warbler. 

 In the adjacent towns I have twice seen a Brewster's Warbler: in Concord, 

 May 19, 1912 (Faxon, Mem. Comp. ZooL, Vol XL, No. 6, p. 312, footnote 

 1), five miles from the Lexington swamp, and in Waltham, May 31, 1915, 

 two miles from the Lexington locahty. — Walter Faxon, Lexington, 



