1374 U.S. NATIONAL MUSEUM BULLETIN 237 part 3 



miculated with clove-brown, * * * Abdomen white, the flanks and 

 crissum washed with wood-brown and duskily streaked." Some 

 individuals acquire a central breast spot. 



The nuptial plumage is acquired by a partial prenuptial molt that 

 begins in late March or early April while the birds are still on the 

 wintering grounds. Most birds complete the molt by late April, 

 although a few birds caught in Algonquin Park early in May 1960 

 were in the last stages of the molt. The extent of the prenuptial molt 

 varies among individuals, but it generally involves feathers of the head, 

 throat, breast, and flanks; also the middle two rectrices and inner 

 three secondaries are sometimes replaced. 



From studies of 706 museum specimens and of 342 live birds breeding 

 in Algonquin Park and sexed by cloacal protuberance (Wolf son, 1952), 

 Lowther (1961, 1962) has shown that the white-throated sparrow is 

 a polymorphic species. The two basic types differ essentially in the 

 color of the median crown stripe, being either white-striped or tan- 

 striped, and both types occur in both sexes. Associated with this 

 dimorphism of the median crown stripe are other color variants. 

 Although the plumage patterns of both types are similar to those of 

 young birds in the first winter plumage, color intensities differ on 

 different parts of the body. Regardless of sex, the white-striped 

 birds are generally brighter colored and less streaked; they have more 

 black on the lateral crown areas, less streaking on a wider and grayer 

 chest band, less intense black on the malar markings of the white 

 throat patch, and brighter yellow on the superciliary stripe; also they 

 tend to have longer wing chords than do tan-striped individuals. 

 A central breast spot occurs more frequently in the tan-striped birds. 



Tan-striped adults are indistinguishable from the majority of im- 

 mature birds in the first winter plumage. 



Every one of 45 immature birds kept in captivity during the winter 

 of 1961-62, including individuals of both types, underwent a pre- 

 nuptial molt during the spring, particularly of the head and anterior 

 body regions. Two additional birds banded as juveniles in 1959 were 

 retrapped as adults in 1960; one was then a white-striped female, 

 the other a tan-striped female. These observations indicate that the 

 white-striped plumage may be attained in the first prenuptial molt. 



Of the birds banded as adults in Algonquin Park in 1959, 1960, 

 and 1961, 46 individuals of both types were recaptured in subsequent 

 years for a total of 56 recaptures. Each of these birds showed the 

 same color in later years as when it was first banded, most notably 

 a tan-striped male banded in 1959 and recaptured in 1962. Similarly 

 Forbush (1929), Hervey Brackbill (1954), and J. T. Nichols (1954, 

 1957) report banded individuals that retained their dull (tan) colora- 

 tion after 2, 2 and 3, and 6K years. Thus the two color types are 



