248 BIRDS OF THE REPUBLIC OF PANAMA PART 2 



usual flexible motion of open and closed wing of other flying birds. 

 This allows controlled movement in all directions, including backward 

 flight, without changing the direction or position of the body, not 

 possible in other birds. 



One curious structural feature is the location of the syrinx on the 

 neck outside the body cavity, with the two long bronchi leading 

 down into the thorax to the lungs. Though this peculiarity was de- 

 scribed by William MacGillivray in 1839 in Audubon's Ornitho- 

 logical Biography, it has been little noticed in accounts of the family. 



The family Trochilidae has long been united as a separate suborder 

 in the Order Apodiformes, which also includes the swifts ; however, 

 as detailed information in the families Apodidae and Trochilidae in- 

 creases, it seems probable that structural and behavioral differences 

 eventually will serve to place these two groups in separate orders. 



KEY TO SPECIES OF TROCHILIDAE 



1. Bill strongly curved, sickle-shapecl. 



Sicklebill, Eutoxcrcs aquila salvini, p. 276 

 Bill straight or slightly curved, not sickle-shaped 2 



2. Under surface, including sides, pure white from chin to under tail coverts 



(throat faintly spotted with pale gray in immature individuals). 



Violet-crowned fairy, Hcliothryx barroti, p. 364 



Under surface of body not entirely pure white, or if white centrally with 



sides spotted prominently with metallic green 3 



3. Under surface grayish white heavily streaked with dusky from throat to 



abdomen Tooth-billed hummingbird, Androdon aequatorialis, p. 254 



Under surface not uniformly streaked 4 



4. Outer tail feathers extensively white 5 



Outer tail feathers with white, if present, restricted to base or tips 9 



5. Very large, wing more than 73 mm. ; bill heavy, strongly curved ; white 



on outer tail feathers covering more than one-third of distal end. 



Violet saberwing, Campylopterus hemileucurus mcllitus, p. 285 

 Small, wing not more than 70 mm. ; bill slender, straight or nearly so. . . 6 



6. A white band across hindneck ; all of outer tail feathers white except for 



narrow dark tip. 



White-necked Jacobin, Florisaga mellivora mellivora, male, p. 287 

 No white band on hindneck 7 



7. Secondaries plain, like primaries ; tail white, tipped rather broadly with 



black White-tailed emerald, Elvira chionura, p. 340 



Secondaries spotted prominently with cinnamon-rufous; this marking less 

 definite in females 8 



8. Larger, wing in males (under surface of body green) more than 57 mm.; 



in females (under surface of body whitish) 54 mm. or more. 



Stripe-tailed hummingbird, Euphcrusa eximia egregia, p. 338 

 Smaller, wing in males (breast black) not more than 51 mm.; in females 

 (under surface of body grayish white) not more than 47 mm. 



Black-bellied hummingbird, Eupherusa nigriventris, p. 339 



