FAMILY TYRANNIDAE 455 



in northern South America. Dr. Allan Phillips points out another 

 character to separate the eastern and western groups in which the 

 distance from the distal end of the longest upper tail covert to the 

 tip of the tail is greater in the eastern vircns than in the assemblage 

 of forms of the west. In addition, the longer song of two or three 

 notes in the eastern birds is more attractive than the shorter, less 

 musical call of those of the west. 



While the two have long been treated as two species, recognized 

 by this difference in voice as well as by their coloration, in the area 

 where their ranges merge, the form of the call appears to intergrade. 

 Mainly because of this, recently some have treated the complex as a 

 single species under the specific name vircns. As this seems still 

 not definitely established the two here are listed as two species. 



Recognition of wood pewees in Panama in the field is complicated 

 further by the presence of a distinct resident species Contopus 

 cinereus, similar superficially in color to vircns, but smaller, and in 

 the hand with a different wing formula. 



CONTOPUS SORDIDULUS Sclater: Western Wood Pewee, 

 Papamoscas Occidental 



Medium size ; like Contopus vircns, but averaging darker, more 

 olive above ; distal end or, in some, all of the mandible dark ; axillars 

 and under wing coverts brown, varying in shade (but not white) ; dis- 

 tance from end of longest upper tail covert to end of tail less ; in 

 general, with the breast band dark gray, only rarely divided in the 

 center ; in most the lower surface whiter. 



The breeding range of the species in western North America ex- 

 tends from central Alaska and Yukon south through western Canada, 

 western United States, Baja California, and the southern mainland 

 of Mexico (Guerrero and Chiapas) and to the highlands of Hon- 

 duras, possibly, but from present data uncertainly, to Nicaragua. It 

 has been reported nesting also in Costa Rica and in western Panama 

 but without basis in definite record. A supposed breeding record in 

 northwestern Colombia (De Schauensee, Caldasia, vol. 5, no. 26, 

 1952, p. 1199) refers to the resident race of Contopus cinereus. ^ 



Two additional forms described recently by Thomas D. Burleigh 

 (Proc. Biol. Soc. Washington, 1960, pp. 141-146) appear to repre- 

 sent two areas of intergradation between the most northern form 

 saturatus and veliei to the south. His proposed C. s. amplus appears 

 close to sotiirotus, and C. s. siccicola to veliei. They require further 

 study with additional material before recognition. 



