456 BULLETIN 17 6, UNITED STATES NATIONAL MUSEUM 



The purpose of so much vocal activity on the part of the males 

 is without much doubt to attract the opposite sex. Their season 

 of song coincides roughly with the nesting period of the females. 

 Yet, in spite of many hours of watching, I was not able to deter- 

 mine the beliavior of the males when a female approached or to 

 witness actual pairing. The white-ears are so small and withal so 

 shy that they are difficult to keep in sight; on the wing their move- 

 ments are so swift that it is impossible to distinguish male from 

 female, or even to follow them long with the eye. I saw three or 

 four of these hummingbirds flying together, pursuing and pursued, 

 so frequently that I suspect that they do not honor the rights of 

 their neighbors when a female approaches, as manakins, which form 

 similar assemblies for courtship, almost invariably do. 



In January, when the blossoms become less abundant with increas- 

 ing drought, the white-ears disperse and cease to call. During 

 most of the year they are silent; and one is not likely to notice them 

 unless he watches before a stand of flowers, which they visit for 

 the purpose of sipping the nectar. 



Nesting. — In the middle of October 1933, six or seven weeks after 

 the males had selected their posts and begun to sing in a tentative 

 fashion, I found a female just beginning her nest. Later I found a 

 dozen more, which, together with four I had discovered in Novem- 

 ber 1930, brought the total up to 17; but some were never com- 

 pleted, all were well removed from the singing assemblies of the 

 males, some far away, others just sufficiently distant to be out of 

 hearing of the nearest male — that is, of course, too far away for ine^ 

 to hear his voice. With a single exception, all these nests were 

 placed among the slender twigs of the raijon {Baccharis vaccini- 

 oides), a composite shrub common everywhere on the mountains, at 

 heights varying from 5 to 20 feet above ground. The one nest not 

 in a raijon bush had been built in the crotch of an ascending branch 

 of a bushy Eupatorium. The nests were situated in bushy clear- 

 ings or light, open woodland. 



The female white-ear built her nest alone, without the assistance 

 or even the encouragement of one of the males that sang so tire- 

 lessly beyond sight and hearing. The raijon bush she chose as its 

 site was never far distant from the oak trees upon which she de- 

 pended for the downy materials she needed. The leaves of sev- 

 eral species, belonging to both the white and black oak groups, are 

 covered on the lower surface with a dense, woolly cloak composed 

 of rather short, crinkled, tawny Imirs. This hairy covering is firmly 

 attached to the epidermis and difficult to remove, except in places 

 where a leaf-mining larva has devoured the underlying tissues. By 

 seeking out the spots where the larva has separated the epidermis 

 from the body of the leaf, the hummingbirds materially diminish the 



