BIRDS OF NORTH AND MIDDLE AMERICA. 817 



KEY TO THE SPECIES AND SUBSPECIES OF SIRYSTES. 



a. Rump light olive or grayish, l>ecoming whitisli or palo yellowish olive on extreme 

 lower portion. {Sinjstes sibilator.) 

 b. Darker above, with lower rump pale yellowish olive or dull pale yellowish; bill 

 larger and tail hmger (adult male, wing 9(1, tail 8fi«). (Paraguay and south- 

 eastern Brazil.) Sirystes sibilator sibilator (extraliniital ) b 



bb. Paler above, with lower rumj) wliitisli; bill smaller, lull .shorter (adult male, 

 wing 90, tail 80, exposed culmen 15.5, tarsus 19). (Southwestern Brazil.) 



Sirystes sibilator atimastus fextralimilal)c 

 ««. Rump (extensively) white. 



b. Wing-coverts narrowly margined (tipped and edged) with grayi.sh. C'oloml)ia, 



Ecuador, and upper Amazon Valley.) Sirystes albocinereus (extralimital ) d 



bb. Wing-coverts broadly margined with white. (Panama.) 



Sirystes albogriseus (p. 817) 



SIRYSTES ALBOGRISEUS (Lawrence) 

 PANAMA SIRYSTES. 



Adult. — Pileiiiii dull black, passino; into dtisky slate color on fore- 

 head and nape, the loral, suborbital, and atiricular regions slate- 

 grayish; liindneck, back, and scapulars light yellowish gray, some 

 of the feathers with indistinct shaft-streaks of darker grayish; rump 

 wliite; shorter upper tail-coverts pale gray broadly margined with 

 grayish wliite, the longer ones deep brownish gray passing into pale 

 gray on margins and with blackish shaft-streaks; tail didl black or 

 dusky narrowly tipped with pale gray, the outermost rectrix nar- 

 rowly edged with dull white; wings dull black, the lesser coverts 



" The above measurements are from Sclater (Cat. Birds Brit. Mus. , xiv, 1888, 181), the 

 only specimens at my disposal being females. One of these (from Sapucay, Paraguay) 

 measures as follows: wing, 93; tail, 85; exposed culmen, 18; tarsus, 20. 



b Muscica pa sibilator YieiWot, Nouv. Diet. d'Hist. Nat., xxi, 1818, 457 (Paraguay; 

 based on Pitador Azara, Apunt., ii, 135). — " M." [i. e., Sirystes] sibilator Cabanis and 

 Heine, Mus. Hein., ii, 1859, 75 (Brazil). — Sirystes sibilator Sclater, Cat. Am.- Birds, 

 1862, 75 (Brazil); Cat. Birds Brit. Mus., xiv, 1888, 181 (Pelotes, Rio Grande do Sul, 

 and Rio Clara, Goyaz, Brazil). — Sirystes sibilator sibilator Oberholser, Proc. IT. S. Nat. 

 Mus., XXV, no. 1276, 1902, 66, in text. — [Pitangiis] sibilator Gray, Hand-list, i, 1869, 

 357, no. 5930. — M[uscicapa] sibilans Lichtenstein, Verz. Doubl., 1823, 54 (Sao Paulo, 

 s. Brazil; based on Le Sillleur Azara, 191). — Tyranniila sibilans Hartlaub, Index 

 Azara's Apunt., 1847, 13. — Myiarckus sibilans Burmeister, Syst. Ueb. Th. Bras., ii, 

 1856, 472.— M[yiobius] sibilans Gray, Gen. Birds, i, 1847, 249. 



<^ Sirystes sibilator (not Muscicapa sibilator Vieillot) Allen, Bull. Am. Mus. N. II., iv, 

 1892, 338 (Chapada, Mattogrosso, Brazil). — Sirystes sibilator atimastus Oberholser, Proc. 

 U. S. Nat. Mus., XXV, no. 1276, Aug. 30, 1902, 66 (Chapada, Mattogrosso, s. w. Brazil; 

 coll. U. S. Nat. Mus.). — S[irystes] albocinereus atimastus Berlepsch, Proc. Fourth In- 

 ternat. Orn. Congr., Feb., 1907, 475. 



d Sirystes albogriseus (not of Lawrence) Sclater and Salvin, Proc. Zool. Soc. Lond., 

 1873, 280 (Santa Cruz, e. Peru; crit.); Taczanowski, Orn. du Perou, ii, 1884, 287. — 

 Sirystes albocinereus Sclater and Salvin, Proc. Zool. Soc. Ltmd., 1880, 156 (Bogota, 

 Colombia; coll. P. L. Sclater); Sclater, Cat. Birds Brit. Mus., xiv, 1888, 181, pi. 14 

 (Bogota; Sarayacu, e. Ecuador; Santa Cruz and Yquitos, e. Peru; Upper Amazons). 



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