i;88 THE PICARIAN BIRDS 



De Oca has observed a similar fact with regard to the wedge-tailed sabre wing. Mr. 

 Ridgway adds that "although the muffled buzzing or humming noise which has 

 given this family of birds its distinctive name is the sound usually accompany- 

 ing the flight of humming birds, the males of some species accompany their flight 

 by a most remarkable noise, of an entirely different character." While among the 

 mountains of Utah, in 1869, the writer was for a long time mystified by a shrill 

 screeching noise, something like that produced by a rapidly revolving circular saw 

 when rubbed by a splinter. This noise was evidently in the air, but I could not 

 trace its origin, until I discovered a humming bird passing through the air over- 

 head in a curious undulating kind of flight. I afterwards heard the same sound 

 produced by males of the same species (the broad-tailed humming bird) when they 

 were driving other birds away from the vicinity of their nests. At such times they 

 would ascend almost perpendicularly to a considerable height, and then descend 

 with the quickness of a flash at the object of their animosity, w r hich was, perhaps, 

 more frightened or annoyed at the accompanying noise than by the attack itself. 

 Mr. F. Stephens calls this the "courtship song," but from the circumstance that, 

 in the broad-tailed humming bird at least, it is often produced by solitary individ- 

 uals while wending their way between distant points, I hardly think that it can be 

 so considered. Mr. Stephens writes of Costa's humming bird that " the female is 

 sitting on a twig in a low bush, not on an exposed twig, as is often the case when 

 she is merely resting; but when the male begins she goes further in, as if she 

 feared that he really intended mischief, while he rises high in the air, and with a 

 headlong swoop comes down, passing her, and, turning with a sharp curve as near 

 her as possible, mounts on high, to repeat the manoeuvre again and again. A 

 shrill whistle is heard as he begins to descend, starting low and becoming louder 

 and louder, until, as he passes her, it becomes a shriek, which is plainly audible for 

 a distance of a hundred yards or more. As he mounts again it dies away, only to 

 be repeated at the next descent. This is a common manreuvre with the species, the 

 whistle made during the descent being quite low." The nests are tiny structures, 

 generally made of moss, and covered externally with lichens, which cause them to 

 resemble the surroundings in which they are placed. The eggs are two in number, 

 white, and oval at both ends. 



Humming birds are divided into three sections, the characteristics of which are 

 not very trenchantly marked, the fact being that these birds form a very homo- 

 geneous group, and thus do not lend themselves to any easily recognizable scheme 

 of classification. The number of species described is nearly five hundred, these 

 being divided into one hundred and twenty-seven genera. In these genera every 

 possible variation of form is perceptible, from the longest to the tiniest bill, the 

 simplest form of tail to the most elaborate of structures, while the metallic plumage, 

 so characteristic of the humming birds in general, is absent in not a few of the gen- 

 era, and the color of the simplest kind. 



The members of this section, as its name implies, are characterized 



lw ~ ea by the serrated cutting edges of the fore part of the upper mandible, 



the corresponding portion of the lower jaw being in some instances 



similarly notched. The group comprises upward of five and twenty genera, the 



