BREWSTER’S WARBLER (HELMINTHOPHILA LEUCOBRONCHIA- 
LIS) A HYBRID BETWEEN THE GOLDEN-WINGED WARBLER 
(HELMINTHOPHILA CHRYSOPTERA) AND THE BLUE- 
WINGED WARBLER (HELMINTHOPHILA PINUS). 
Tue real nature of Brewster’s Warbler has long been a moot point with 
ornithologists. Is it a true species, a mongrel, a color-phase of the Blue-winged 
Warbler, or an atavistic form of the Golden-winged Warbler? Each of the four 
propositions implied in this question has found advocates among the various 
authors who have written on the topic, but until now no indubitable proof of 
the true status of this bird has been obtained. 
In January, 1911, I published a paper bearing on this subject, in the Memoirs 
of the Museum of Comparative Zoélogy, 40, no. 2; I will here give a résumé 
of the facts recorded in it, a course which seems desirable because these facts 
were misstated by the reviewer of my article, in The Auk for April, 1911. 
In the summer of 1910, there bred within the confines of a swamp of about 
fifteen acres in Lexington, Mass., a pair of Golden-winged Warblers, and two 
male Golden-winged Warblers mated with two female Brewster’s Warblers. 
In the same swamp there was also a male Brewster’s Warbler that unquestion- 
ably was unmated. The progeny of the three pairs were closely observed from 
the juvenile (in one case, from the natal) plumage up to the first winter plumage, 
when the adult characters were acquired; the young of the pair of Golden-wings 
were all Golden-wings; one of the Brewster’s Warblers that was mated with a 
Golden-wing brought forth a homogeneous brood of Brewster’s Warblers, while 
the other produced a mixed brood of Brewster’s Warblers and at least one Golden- 
winged Warbler. A striking thing about it was this: the young birds of mixed 
parentage were absolutely pure in plumage,— either Brewster’s Warblers or 
Golden-wings, without any tendency to combine, as “‘intermediates,”’ the char- 
acters of the two parents. They appeared to exemplify the transmission of 
characters in accordance with Mendel’s Law, and from that time I had little 
doubt that Brewster’s Warbler itself would prove to be a result of the union 
