434 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



tion to himself. Among many species, the males group themselves 

 into assemblies made up of two to many individuals, but frequently 

 they are found "singing" alone. This "static" form of courtship 

 is far more prevalent among the Central American hummingbirds 

 than the set aerial display. So far as we know, the same species 

 does not practice both types of courtship. 



The courtship of Rieffer's hummingbird is neither persistent nor 

 likely to draw the bird-watcher's attention. In a number of years 

 past, in districts where the species is abundant, I liave not once 

 witnessed an aerial display of definite form comparable to that of 

 the broad-tailed hummingbird. So far as it has any particular mode 

 of courtship, this appears to be of the "static" type; but even in 

 the less arduous occupation of sitting and calling, Rieffer's humming- 

 bird is far less assiduous than many others of the Central American 

 species. The scanty information I have on this subject is sum- 

 marized in an entry made in my notebook on October 17, 1936, 

 while I lived at Rivas de El General, in southwestern Costa Rica: 



"These m.ornings, when I stand in the old cornfield at dawn to 

 watch the golden-naped woodpeckers arise, I hear the quaint little 

 songs of the Rieffer's hummingbirds. This morning I distinctly 

 heard three of them, apparently situated at different points along the 

 edge of the forest, at the head of the clearing. The one I watched 

 was perching on a twig in the top of a fallen tree, 6 feet above 

 ground, just outside the edge of the forest. The 'song' is quite 

 distinct from that of any other hummingbird that I know, and easy 

 to recognize once it has been heard ; but as usual with hummingbirds' 

 songs, I find it difficult to paraphrase in human words, or to describe 

 it in such a fashion as to give anyone who has not heard it a notion 

 of its quaint pleasantness. Tse-we ts' toe is as near as I can come 

 to it in alphabetical notation ; but I am not well satisfied with what 

 I have written. Sometimes the phrase is repeated several times con- 

 tinuously ; sometimes the bird sings Tse-we ts' we tse-xoe. These hum- 

 mingbirds sing most actively in the dawn, and less and less as the 

 day grows older. 



"I first heard Rieffer's hummingbirds singing here last December, 

 when I watched a bird that perched very near the position of the 

 one I watched this morning. Probably he was the same individual. 

 During the greater part of the dry season I failed to notice the odd 

 little song; but now it has been a month or so since it was resumed. 

 The males seem to have a singing assembly here at the edge of the 

 forest, where they are to be found every morning; but they perform 

 less constantly than many other kinds of hummingbirds." 



Nesting. — In the Caribbean lowlands of Central America Rieffer's 

 hummingbird has been found nesting at all seasons, and there are 



