BREWSTER'S WARBLER (HELMINTHOPHILA LEUCOBEONCHIA- 

 LIS) A HYBRID BETWEEN THE GOLDEN-WINGED WARBLER 

 (HELMINTHOPHILA CHRYSOPTERA) AND THE BLUE- 

 WINGED WARBLER {HELMINTHOPHILA PINUS). 



The 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 tlie 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, 1911,1 published a paper bearing on this subject, in the Memoirs 

 of the Museum of Comparative Zoology, 40, no. 2; I will here give a restmie 

 of the facts recorded in it, a course which seems desirable because these facts 

 were misstated by the re\iewer 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 lirood 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 



