White-throated Swift 251 



and other vegetable matter and a few feathers, all glued 

 together with hardened saliva. The eggs, four or five, 

 are white and measure 87 x '52. 



A female shot by Drew, June 20th, at 13,000 feet near 

 Silverton, contained an egg ready for extrusion ; while 

 Gale, though he apparently never actually took eggs 

 of this species, gives May 25th to June 10th as the date 

 for fresh eggs in Boulder co. 



Family TROCHILIDiE. 



The Humming-birds which make up this family hardly 

 require a diagnosis ; their tiny size and their metallic 

 colouring at once distinguish them. The bill is very 

 long and slender and usually straight, the nostrils are 

 linear and protected by an overhanging scale or oper- 

 culum, and often feathered and concealed ; the wing is 

 long and consists of ten elongated and often curiously 

 attenuated primaries, and six reduced and very short 

 secondaries ; the tail consists of ten rectrices ; the feet 

 are extremely small and weak, and only adapted to 

 perching. 



The following Key separates the Species found in Colobado. 



A. Tail not white-tipped (males). 



a. Back chiefly rufous, gorget coppery-red. S. rufus, <? p. 255. 



b. Back and central tail-feathers green. 



a^ Tail rufous at the base, gorget crimson. 



S. platycercus, $ p. 253. 

 b^ Tail without rufous ; gorget dusky purpUsh. 



A. alexandri, S p. 252. 



c. Back green, central tail-feathers dusky. S. calliope, $ p. 256. 



B. Tail white-tipped (females). 



a. No visible rufous at the base of the tail. 



a^ Tail-feathers obtusely pointed ; no rufous on the flanks. 



A. alexandri, $ p. 252. 



b^ Tail-feathers spoon-shaped and rounded, flanks slightly 



washed with rufous. S. calliope, ? p. 256. 



