RRKWSTEH'S WARIiLER. 315 



The history of iho otlior i)air in tho swamp, a male Brewster's Warbler and 

 a female Ciolden-win^', may l)p told in a lew words. As in one of tlie two cases 

 of a male Golden-wing joined with a iVnialc Brewster's Warbler, considered in 

 detail in my memoir published in 1911, a majority of their issue were Brewster's 

 Warblers, but one of them a male (!oIden-wing. Dr. Tyler banded two of the 

 little birds belonging to this brood on the 19th of June, when they were but a day 

 or two out of the nest and as like each other as two peas from one pod; one of 

 these grew up to be a typical Brewster's Warbler while the other, its own brother, 

 became a typical male Golden-wing. If any of the birds that were banded 

 (three in all) return and breed in their native place next summer, we may be 

 able to establish a family pedigree for these interesting hybrids, extending 

 through three generations, complete as regards both the male and the female 

 lines. 



In nn' paper published in 1911, after stating the different hypotheses pro- 

 posed in order to explain the relations existing among the Golden-winged, Blue- 

 winged, Brewster's, and Lawrence's Warblers I added, half in jest, that the only 

 hypothesis left for a new-comer in the field was this: that the Golden-winged 

 and the Blue-winged Warblers themselves were merely two forms of one species. 

 Curiously enough, not long after this I found that this very opinion had been 

 expressed, and in a most unexpected quarter: in a letter dated Edinburgh, 

 Sept. 15, 1835, Audubon wrote to Bachman that he suspected the Golden- 

 W'inged Warbler and the Blue-winged Warbler were one species ! ' That Audubon 

 at that early date, ignorant (as he was assumed to be) of the existence of 

 Brewster's and Lawrence's Warblers, and but superficially acquainted with the 

 Golden-wing, should suspect that two birds so diverse as the Blue-wing and 

 the Golden-wing were one species seemed incomprehensible, and in the light of 

 what we now know about these birds, his surmise seemed to presuppose an 

 almost superhuman faculty of prevision. 



As a possible explanation of Audubon's letter I have only this to offer: 

 in the winter of 1876-77 Dr. Spencer Trotter - discovered in the collection of the 

 Academy of Natural Sciences of Philadelphia a specimen of Brewster's Warbler 

 without a label, the third specimen known up to that time; on the bottom of 



'This letter is amony; the many unpuhhshed MS. letters of Audubon in the Wade eoUeetion, 

 generously presented to this Museum by Mr. John E. Thayer. 



2See Proc. Acad. Nat. Sei. Phila. for 1877, Jan. 1, 1878, p. 292; Bull. Nuttall Ornithol. Club, 

 Jan., 1878, 3, p. 44, Jan., 1879, 4, p. 59. 



