FAMILY VIREONIDAE 



197 



usually a monotonous warble or whistle, are given throughout the day 

 and make these birds easy to find. All vireos, so far as known, build 

 cup-shaped nests suspended in a forked branch in trees or shrubs. Six- 

 teen species, including 1 peppershrike and 2 shrike-vireos, have been 

 found in Panama. Six species in the genus Vireo occur in Panama as 

 migrants or winterers from the north. The Yellow-green Vireo ( Vireo 

 flavoviridis) on the other hand is the only songbird that nests in Pan- 

 ama and "winters" elsewhere. The other Panamanian species of vireos 

 are permanent residents. 



KEY TO SPECIES OF VIREONIDAE 



1. Rufous stripe above eye. 



Rufous-browed Peppershrike, Cyclarhis gujanensis. p. 198 



No rufous stripe over eye 2 



2. Light blue on crown 3 



No light blue on crown 4 



3. Yellow superciliary. 



Yellow-browed Shrike- Vireo, Smaragdolanius eximius. p. 208 

 No superciliary. 



Green Shrike- Vireo, Smaragdolanius pulchellus. p. 204 



4. Wing bars present 5 



Wing bars absent 7 



5. Throat bright yellow. 



Yellow-throated Vireo, Vireo flavifrons. p. 213 

 Throat whitish or pale yellow 6 



6. Wing bars yellowish, partial eye-ring yellowish to white. 



Yellow- winged Vireo, Vireo carmioli. p. 211 

 Wing bars white, supra-loral stripe white. 



W r hite-eyed Vireo, Vireo griseus noveboracensis. p. 210 



7. Superciliary present 8 



Superciliary absent 12 



8. Dusky moustachial stripe. 



Black-whiskered Vireo, Vireo altiloquus. p. 221 

 No moustachial stripe 9 



9. Undersurface entirely or partially yellow 10 



Undersurface entirely white (sometimes pale yellowish wash on flanks). 



Red-eyed Vireo, Vireo olivaceus. p. 215 



10. Center of undersurface white, sides greenish yellow. 



Yellow-green Vireo, Vireo flavoviridis flavoviridis. p. 217 

 Most of undersurface pale yellow 11 



11. Crown definitely brown, contrasting with more greenish back. 



Warbling Vireo, Vireo gilvus. p. 225 

 Crown grayish olive, same color as back. 



Philadelphia Vireo, Vireo philadelphicus. p. 223 



12. Undersurface mostly white. 



Lesser Greenlet, Hylophilus decurtatus. p. 228 



