BROAD-BILLED HUMMINGBIRD 467 



molded the bottom of it with quivering, caressing motions of the body. 

 Often in the process the wings revolved at almost full velocity, cer- 

 tainly until they were blurred to sight, and yet the body of the bird 

 appeared to be sitting in the nest throughout the action. I saw it 

 performed a number of times; sometimes it gave the impression of 

 a swaying motion, from one side to the other, without the body leav- 

 ing the nest, or the wings ceasing to revolve. When the wings did 

 not revolve, the bill moved rapidly along the outside of the abode, 

 tucking in protruding ends of grasses. 



"The bulk of the nest is composed of exceedingly fine material, 

 mostly tiny shreds of buff-colored or brownish bark, grasses, and bits 

 of dried leaves. The only larger pieces are three strips of bark 

 placed upright, parallel with the tiny twig on which the nest is placed. 

 I imagine these came from the sabino, a cypress that grows to a great 

 height along a small stream not far away. Part of the inside of the 

 nest is lined with a white material, probably some kind of minute 

 plant down, but possibly cotton of fine texture. All these materials 

 could be obtained from the fields nearby, which are cultivated by the 

 Indian's of the Guirocoba Plantation, 



"Three other nests were secured by our expedition in Sinaloa, two 

 of them in March at Culiacan and one on January 16, 1936, at San 

 Lorenzo, Sinaloa. Examination of the sex organs of our numerous 

 specimens proves that the birds are apt to breed at any time from 

 January to August. 



"As these last three nests contain two eggs each, it can be presumed 

 that they are finished creations, although some hummingbirds attach 

 ornamental bits of lichen to the exterior, even during the period of 

 incubation. Not the slightest indication of this appears in any of 

 these four nests. The January nest was taken at San Lorenzo by 

 Chester C. Lamb, which differs somewhat from the other three. Like 

 the March 1 nest, it was attached to the stalk of a vine. Placed 4 

 feet up in an espino tree, the body of the nest is composed almost 

 entirely of cotton, but lined with a glossy-white plant down. The 

 base is supported by a dried pod of the vine itself. On the outside 

 are attached pieces of dried leaves and, according to Mr. Lamb, some 

 'short fibers of the palo-blanco pods.' The entire exterior is bound 

 together with spiderwebs. The March 1 and March 7 nests from 

 Culiacan display a lining of white plant down, covered on the periph- 

 ery with bits of bark and leaves, but the bodies of the nests seem to 

 be made of grasses and exceedingly fine, threadlike stalks of dried 

 plants. The March 1 nest was placed in a 'dry bush, covered with 

 dry vines' and the March 7 in an espino tree. 



"In spite of these minor differences, these abodes are so similar that 

 I think I could recognize them at random among a large number of 

 other hummingbird nests. They all have some grass stalks in the 



