RIEFFER'S HUMMINGBIRD 439 



mala I once found a nest containing eggs, built upon an older nest 

 of the same kind that had turned sideways. 



Eggs. — As with the great majority of hummingbirds, Rieffer's lays 

 two eggs. The interval between the laying of the first and second is 

 two days (about 48 hours). The eggs are pure white and oblong or 

 oblong-ovate, often with little difference between the two ends. The 

 measurements of six eggs removed temporarily from their nests in 

 Honduras average 14 by 8.7 millimeters; the eggs showing the four 

 extremes measure 14.2 by 8.6, 14 by 9.1, and 13.5 by 8.6 millimeters. 



Young. — As she builds, so the female hummingbird incubates quite 

 alone ; and no male of her kind takes an interest in her labors. Dur- 

 ing her recesses she continues to seek fresh downy material and cob- 

 web to add to her nest, even when it is already well padded. The 

 period of incubation is normally 16 days. I have never enjoyed a 

 better opportunity to watch the care and development of the young 

 than was offered by the nest in the ramie plant, just outside the 

 window before my work table in Panama. 



The newly emerged nestlings were like ugly grubs, blind, black- 

 skinned, and naked except for two lines of short, tawny down ex- 

 tending the length of the back, one on each side of the middle line. 

 The slender bill of the adult was represented by a mere bump, hardly 

 longer than that of a newly hatched pauraque {Nyctidroirms alhi- 

 collis). At intervals one of the graceless creatures reared up spas- 

 modically, opening wide its yellow-lined mouth in a voiceless call for 

 nourishment, to sink again exhausted, w'ith drooping head, into the 

 nest. The mother's time for the first week was divided between 

 brooding and feeding her offspring, which she did in the customary 

 manner of the family, by regurgitation. Sitting upright on the rim 

 of the nest, she thrust the rapierlike bill into the nearest gaping 

 mouth, pushing it down until it seemed that it must pierce the en- 

 trails of the nestling. Then with a convulsive jerking of the body 

 she regurgitated a portion of the contents of her crop into that of 

 her infant. Both nestlings were as a rule fed at each return to the 

 nest, and often each was given food twice, alternately. When the 

 nestlings are older, sometimes each is fed four times at a single visit 

 of their mother. After feeding, she usually returned to brooding, 

 repeatedly thrusting out her long, white tongue as she sat on the 

 nest. Although during the day she flew off, twittering her complaint, 

 at my too near approach, at night she would permit me to advance 

 and touch her on the nest, in the beam of a flashlight. 



With these constant ministrations the youngsters grew amazingly, 

 and at the age of six days, when the beady black eyes first began to 

 peep out of the still-naked head, and the bill had lengthened consid- 

 erably, they quite filled the bottom of their downy cup. The next 



