COSTA'S HUMMINGBIRD 367 



indifference, they are likely to leave on very slight provocation. A person may 

 be quietly standing and watching them when as with one impulse both spring 

 from the nest and fly in different directions. It sometimes so happens that 

 the younger of the two is thus induced to venture forth before its wings are 

 capable of sustained flight or of enabling it to obtain a foothold in a tree. On 

 two such occasions I found that the bird might readily be picked up and when 

 restored to its nest gladly settled itself to await more adequate strength. 



The young Hummingbirds are fed by regurgitation, of necessity, at intervals 

 of about half an hour. The feeding requires perhaps half a minute in all and 

 is accomplished by a violent pumping process, with the bill thrust deep into the 

 open mouth of the young bird. One would not judge that the slow growth of 

 the Hummingbird was due to inability to supply sufficient food, since the mother, 

 though bearing the entire care of her offspring, does not seem overworked, but 

 has plenty of time to rest, preen her plumage and engage in skirmishes with 

 other Hummers. Her care of the young continues for some time after they 

 have left the nest. Then their call for food may be heard at intervals, a shrill 

 cheep resembling the cries of other young birds rather than fhe voice of the 

 adult Hummingbird. After the young have attained their full growth in other 

 respects, they may still be recognized by the comparative shortness and straight, 

 subulate form of the bill. 



Major Bendire (1895) quotes K. H. Lawrence, regarding the feed- 

 ing of the young, as follows : 



She fed the young by touching the point of her bill to the tips and sides of 

 the bills of her youngsters, as if to urge or invite them to stir and open their 

 mouths, not inserting her bill over one-fifth or one-fourth of its length. Once 

 she thrust it down half its length into the throat of one nestling, who then 

 clung to it to the very last moment of its withdrawal, apparently reluctant to 

 let the very smallest particle of the regurgitated food miss its way or remain on 

 the parent's bill. The performance was rather ludicrous, as both old and young, 

 especially the youngsters, went through many wriggling and squirming mo- 

 tions. * * * Once, upon her return, settling down to brood the youngsters, 

 she kept up for some moments a kind of paddling motion, as if she were giving 

 them a little massage treatment. Her respiration was very rapid after this 

 exertion. Life with these atoms of sensitiveness must be at a white heat 

 always. The young were lying side by side, but headed in opposite directions. 

 Both had voided excrement in one case, but the parent did not remove either 

 deposit while I was there. Except for this and a piece of eggshell, the nest 

 appeared clean. 



Plumages. — The young Costa's hummingbird is hatched blind and 

 nearly naked; at first there is only a narrow line of pale, yellowish 

 down along each side of the back; this spreads within a few days to 

 cover the back, wings, and top of the head, through which the juvenal 

 plumage later appears ; and at the end of twelve days, they are fairly 

 well feathered (Wheelock, 1904). 



In full juvenal plumage, the young male is much like the adult 

 female, but the feathers of the upper parts are more or less margined 

 with grayish buff; the tail is double rounded, instead of wholly 

 rounded ; the throat is spotted with dusky, most heavily on the sides ; 

 and there are usually some, often many, violet-purple feathers on 



