438 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



up and down I concluded she must be kneading the material to- 

 gether with her toes, although, as they were hidden beneath her, I was 

 unable to see them in action. Sometimes she would dart away and 

 then, as if the kneading and shaping had not been done to her satis- 

 faction, return wdth empty bill to continue the moulding operations. 

 So, as the nest grew, it became just large enough to fit snugly about 

 the central portion of her body, leaving neck and head and rump and 

 tail protruding beyond its rim. 



Hummingbirds of this species do not seem to have any prescribed 

 order for the addition of the various elements of which the nest is 

 composed. This particular bird began with a wad of down, then 

 bound around it strips of fibrous vegetable material, such as grass 

 blades softened by partial decay, and fastened them there with cob- 

 web. Others begin with strips of grass and banana-leaf epidermis, 

 adding the down later when they can get it. It seems to be merely 

 a matter of convenience or luck in finding the proper materials. 

 I once found a nest built entirely of fine grass and pieces of w^eeds 

 but so devoid of lining that the eggs touched the branch on which 

 it rested. This was doubtless because down for the lining was not 

 available ; and under favorable conditions the downy lining is added 

 simultaneously with the fibrous materials, which impart rigidity to 

 the structure. Although the lichens and mosses appear to be merely 

 an ornament of the nest, and do not constitute an essential part of 

 the structure, they are often added before the foundation portions 6i 

 the walls are completed. 



Because of torrential rains that interrupted her work, this hum- 

 mingbird required 12 days for the completion of her nest; but 

 others, building during more favorable weather, may finish their 

 task in a week. 



The attachment of Rieffer's hummingbird to a nest site once chosen 

 is very strong. Soon after the eggs had hatched in the nest whose 

 construction has been described, the nestlings were attacked and 

 killed by ants. The deserted nest was then used as a quarry by an- 

 other hummingbird, who removed most of the down to her own new 

 structure on the opposite side of the building. Six weeks after the 

 destruction of the nestlings, all that remained of their nest was its 

 basal portion, a shallow cup of grass and fibers with hardly any 

 lining, darkened and discolored by the elements. The original 

 builder now reclaimed it, added fresh bits of grass to the walls, in- 

 creasing their height, and attached new lichens to the exterior. 

 With the nest in this condition, she laid her two eggs upon the hard, 

 impacted bottom; but afterward, in the intervals of incubation, she 

 continued to build up and line the old structure, until at length it 

 was as comfortable, and appeared as solid, as when new. In Guate- 



