BLACK-CHINNED HUMMINGBIRD 357 



The nest shown on plate 58 illustrates the durability of the ap- 

 parently fragile material used in its construction; it was composed 

 exclusively of plant down firmly bound with cobwebs, and had served 

 for the rearing of two young, meanwhile experiencing three 11-hour 

 overhead irrigations. 



Eoy W. Quillin writes to me from Bexar County, Tex. : "All the 

 nests I have seen were made of plant down of various colors and 

 plastered on the outside with tiny lichens, very much like the nest 

 of the rubythroat. They are totally different from nests of this 

 si3ecies that I have examined from California. The fact that the 

 nest of the blackchin, in this locality, is much like that of the 

 rubythroat and the fact that the latter species is in migration here 

 when the blackchin is nesting have caused records of the nesting 

 of the rubythroat to be printed for Bexar County. I do not think 

 it nests here." 



Eggs. — ^The black-chinned hummingbird lays ordinarily two eggs, 

 but several sets of three have been found, and occasionally a single 

 'ig'g is incubated. The eggs are much like those of the ruby-throated 

 hummingbird but average a trifle smaller; they are about elliptical- 

 oval, pure white, and without gloss. Often two and sometimes three 

 broods are raised in a season. The measurements of 52 eggs average 

 12.51 by 8.30 millimeters ; the eggs showing the four extremes measure 

 13.72 by 8.64, 13.21 by 8.89, 11.68 by 8.13, and 12.19 by 7.87 millimeters. 



Young. — The period of incubation, performed by the female only, 

 is said to be about 13 days. Mary Beal (1933) writes of the young: 



At feeding-time they looked like pale yellow-brown caterpillars with widely 

 gaping mouths, stretching up hungrily. Mother Hummer left the nest every 

 fifteen minutes, and each alternate time on her return she fed the babies, 

 thrusting her long bill down their throats until I held my breath lest she'd 

 punch a hole through them, and every time I breathed a sigh of relief when it 

 was safely over. 



They grew amazingly fast. In a week they made quite a respectable aj)- 

 pearance, and at the end of two weeks they were beautiful, shapely birdlings, 

 completely filling the nest. * * * 



On the nineteenth day, the babies perched on the edge of the nest and 

 tried their wings with a quick humming motion just like Mother's, but they 

 made no attempt to lift themselves into the air. They were still fed as 

 regularly as clockwork, every half hour. 



The day they were three weeks old, they left the nest, flying about with a 

 smart little air of importance, giving thin squeaks of excitement. 



The care and feeding of the young seem to depend entirely on 

 the female, as well as the building of the nest. The male is seldom 

 seen even in the vicinity of the nest. 



Plumages. — The naked young soon begin to acquire a nestling, or 

 Juvenal, plumage and are fully fledged before the}^ leave the nest at 

 the age of about three wrecks. The nestling has a much shorter bill 

 than the adult; the crown is a mixture of graj'ish buff and dusky; 



