Notes on the Plumage of North American Birds 



FORTIETH PAPER 

 By FRANK M. CHAPMAN 



(See frontispiece) 



Sennett's Thrasher [Toxostoma longirostre sennetti, Fig. i). — Sennett's 

 Thrasher is a Texan race of the Mexican Long-billed Thrasher {T. longirostre) 

 and is probably the form from which our Brown Thrasher has been derived. 

 It is not so rufous above, and the bill is longer and more curved than in our 

 Thrasher, but the resemblances in plumage, habit and song between the two 

 are so strong that we are warranted in believing them to be representative 

 of each other. 



The sexes are alike in color, and the limited seasonal changes in color are 

 due chiefly to wear and exposure. 



San Lucas Thrasher (Toxostoma cinereum, Fig. 2). — The sexes are alike 

 in color in this species, and the slight seasonal variations in plumage are due 

 to wear and fading. The juvenal plumage is browner above and more finely 

 streaked below. Among our Thrashers, this species is distinguished by the 

 width of the white marks at the ends of the tail-feathers. 



Two races of the San Lucas Thrasher are known. Both are confined to 

 Lower California, one (T. c. cinereum) being found in the Cape region, the other 

 {T. c. mearnsi) to the west-central coast in the vicinity of San Quentin Bay. 



Bendire's Thrasher (Toxostoma bendirei, Fig. 3). — As with the preceding 

 species, the sexes in Bendire's Thrasher are alike in color, and the small amount 

 of seasonal change is occasioned by wear and fading. In very worn plumage 

 the wing-bars are not evident and the spots on the under parts are barely 

 observable. 



Curve-billed Thrasher (Toxostoma curvirostre, Fig. 4). — As with other 

 Thrashers, the sexes in this species are alike in color, and but little variation 

 in plumage occurs through the year. In worn summer dress the wing-bars 

 and spots on the underparts are not evident. The nestling has the lower back 

 and rump decidedly browner, the markings on the underparts more streaked 

 than in the adult. The tail-feathers have ill-defined brownish tips which seem 

 to fade cjuickly, leaving the feathers merely paler at the ends and, in Palmer's 

 Thrasher at least, with no trace of white. 



Two races of this species are found in the United States, both being mainly 

 restricted to our Mexican border. The Curve-billed Thrasher (T. c. curvirostre) 

 occurs from southeastern New Mexico to the lower Rio Grande Valley, and 

 southward; Palmer's Thrasher {T . c. palmeri), from southwestern New Mexico 

 and west-central Arizona southward. There are two additional races in 

 Mexico. 



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