1914] Grin mil : Mammals and Birds of the Colorado Valley 145 



of ironwoods in washes near Pilot Knob, May 13. The breeding season 

 of this hummingbird in this region is thus definitely indicated and 

 shows itself to be just about one month earlier than on the Pacific slope 

 of southern California. 



Of the nests above referred to, one was placed eight feet above 

 the ground on a dead willow twig, in a close-set grove of tall willows. 

 The other was four feet above the ground on a slanting dead stalk of 

 arrowweed beneath a large spreading willow. In structure and com- 

 position the nests are of the compact type peculiar to this species as 

 compared with those of the Costa. The body of the nest in one (no. 

 769) is closely felted cottonwood and willow down. The whole outer 

 surface is closely beset with small yellow and green leaves gathered 

 where dried, on the lower portions of arrowweed stalks, and attached 

 with web. A conspicuous feature is the extreme constriction of the 

 rim, as shown in the accompanying sectional diagram (fig. G) . Even if 

 the supporting stalk were bent down to a horizontal position, there 

 would be no likelihood of eggs or young falling out, because of the 

 depth of the cavity and narrowing of the neck at the top. This max- 

 imum in complexity of construction, accompanying, as it does, situation 

 upon a tall, slender, and easily swayed stalk, shows marked adaptation 

 in the habits of the bird to meet the special conditions imposed by its 

 nesting site. 



The four newly hatched young (numbered 13985, 13986) are of 

 interest in one particular in that they show a double row of down 

 filaments along the dorsal tract, thus indicating the presence of a 

 partial natal plumage, which plumage has been supposed to be unrepre- 

 sented in the Trochilidae. 



Eighteen adult examples of the black-chinned hummingbird were 

 preserved, nos. 12794—12811. 



There is also in the Museum a skin (no. 5882) taken by W. W. 

 Holder at "Mineral City" (=Ehrenberg) March 20, 1864. 



Calypte costae (Bourcier) 

 Costa Hummingbird 

 First seen February 26, a male Hying northward near Mellen, 

 Arizona. Next noted March 1, opposite The Needles, and for the 

 andersoni which were at this time profusely laden with flowers. A 

 succeeding week very common along ravines on both sides of the river 

 at The Needles. They were feeding about the spiny bushes of Lycium 

 andersoni which were at this time profusely laden with flowers. A 



