Notes on the Plumage of North American Birds 



FORTY-THIRD PAPER 

 By FRANK M. CHAPMAN 



(See frontispiece) 



As Mr. W. DeW. Miller has remarked in discussing the plumage changes 

 of the Wrens figured in Bird-Lore for December, 1916, the sexes in this family 

 are alike in color or essentially so. After the postjuvenal molt, the young bird 

 is distinguishable from the adult only by sHght differences in the wings and tail 

 which are not renewed at that molt, and subsequent changes in the color of 

 the plumage are due only to wear and fading. But if the Wrens vary but little 

 with age, sex, or season, many of the species vary geographically, and those 

 which have a wide range are usually represented in it by a large number of 

 local races or subspecies which, in their color and size, exhibit the effect of the 

 existing environment. 



Bewick's Wren (Thryom-anes bewicki, Fig. i). — The nesting (juvenal) 

 plumage has the breast mottled or indefinitely spotted with blackish, but these 

 markings are lost at the postjuvenal molt, after which the young bird resembles 

 the adult. 



Bewick's Wren is found throughout the greater part of the United States 

 (though it is only locally common east of the Alleghanies) , and is consequently 

 subjected to a wide variety of conditions to which it responds by more or less 

 evident racial variations in color and size. 



Mr. H. C. Oberholser in a review of this group pubhshed in 1899 (Proc. 

 U. S. N. M., XXI, pp. 421-450) includes eleven forms of Bewick's Wren 

 from the United States, Lower California, and the islands of the Pacific coast, 

 but of these the 'Check-List' of the American Ornithologists' Union (1910 Ed.) 

 recognizes only eight. In the latest paper on these Wrens, however, Mr. H. S. 

 Swarth describes no less than eight races from California alone (Proc. Calif. 

 Acad. Sciences, VI, 1916, pp. 53-85). 



Fortunately, these Wrens are as a rule non-migratory, and one therefore 

 rarely finds two races in the same locality. Field identification, therefore, so 

 far as subspecies is concerned, is more a matter of geography than of ornithol- 

 ogy. So far as species is concerned, Bewick's Wren may be readily distin- 

 guished from the House Wren by its white or buffy superciliary line, by its 

 longer tail, larger size and other characters. Our figure, based on the eastern 

 race, is somewhat too rufous and the superciliary line is more buffy than is 

 usual. The western races are grayer, less reddish brown above. 



House Wren (Troglodytes aedon, Fig. 2). — The juvenal plumage differs 

 from that of the adult in the blackish mottling of the breast, but, as with 

 Bewick's Wren, these markings disappear with the postjuvenal molt. It also 

 agrees with that species in having no spring molt, and the breeding plumage is 

 essentially like that worn in winter. 



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