458 BULLETIlSr 17 6, UNITED STATES NATIONAL MUSEUM 



internal dimensions are actually less than either, namely 1 by f^ 

 inch. The internal depth, however, is almost twice as great as that 

 of nest No. 1. The external measurements are length Si/g, width 

 21/4, and depth 2i/s inches. Furthermore, the structure of the external 

 part of the nest is almost totally different, being completely swathed 

 with a fine green moss, and having pine needles, dried twigs, and four 

 or five small leaves, as well as a few lichens, woven into the external 

 construction. There is no evidence whatever that this is a double nest. 



"It is quite probable that the environment of the nest site had a 

 great deal to do with the type of construction. This moss-covered 

 abode was placed on a small shrub, growing out of rocks 4 feet up 

 from the base of a cliff in a very dark and deep arroyo. In such a 

 place much moss is available, whereas lichens are difficult to find. 

 Three nest sites so dissimilar could hardly have been chosen as these 

 three structures — an oak tree on the very highest point of a wind- 

 blown mountain range, a cliff jutting out on the shore of a wind- 

 protected small lake, and the bottom of a deeply shaded gorge. Dis- 

 similarity of nesting period is also indicated — March, May, and 

 August." 



Eggs. — The number of eggs laid by the white-eared hummingbird 

 appears invariably to be two. They are pure white and narrowly 

 oblong. The measurements of six eggs, removed temporarily from 

 their nests in the highlands of Guatemala, average 12.5 by 8.0 milli- 

 meters. The eggs showing the four extremes measure 12.7 by 7.9, 12.3 

 by 8.3, and 11.9 by 7.9 millimeters. 



Young. — Incubation is carried on by the female alone, without 

 ever so much as a visit from on© of the males, which continue to 

 sing as if oblivious of all the cares and labor of the other sex. Both 

 of the female white-ears I watched sat deeply in their nests. When 

 perfectly at rest, the eyes were only a trifle above the rim, the sides 

 were entirely protected, the back was invisible to a person slightly 

 below the level of the nest, while the tail and the tips of the longest 

 wing plumes projected beyond the rim at the rear. They were far 

 better protected than the Rieffer's hummingbirds of the warm low- 

 lands, for the nests of these are comparatively broad and shallow, 

 and much of the body of the sitting bird remains on the outside. 



The white-eared hummingbirds' mode of entering and leaving their 

 nests demonstrated clearly their lightness and skill upon the wing. 

 Upon returning to their eggs after a recess, heavier birds alight upon 

 the rim of the nest, or even upon a branch at a little distance, and 

 walk or hop into the cup. The white-ears never alighted on the rim 

 but invariably flew directly into the nest and, as they settled neatly 

 over the eggs, folded their wings about them and were at once at 

 rest. Most birds of other families, when they wish to leave the nest, 



