548 BULLETIN 20 3, UNITED STATES NATIONAL MUSEUM 



was not completed until June 12, a case, according to Porter, in 

 which the deposit of the eggs was greatly prolonged by cold weather. 



Unlike many birds, the northern yellowthroat usually leaves the 

 nest unobtrusively when a human intruder comes near and does not 

 betray its location by scolding. In the case of one nest the female 

 sat very closely, and by exercising care I was able to almost touch her 

 before she slipped off, mouse-fashion. She crept silently through 

 the grass to the shelter of the neighboring vegetation and from there 

 watched me intently. On another occasion the reaction of a yellow- 

 throat was very different in respect to a small dog. Both birds made 

 a wild demonstration, calling and scolding loudly and even making 

 passes at the intruder in their efforts to drive him away from the 

 vicinity of the nest. 



The birds readily adapt themselves to a blind placed close to the 

 nest, although their suspicions may be aroused at first. A day after 

 the blind is in place they pay little attention to it, and I have had the 

 bird return within 20 minutes after I had entered the structure. 



Young. — The young at the time of hatching are nearly naked, hav- 

 ing only scant tufts of grayish or mouse-colored down on the crown 

 and dorsal tracts of the body and wings. The eyes are sealed shut. 

 Soon after emerging from the eggs the young are active and open 

 wide their mouths in anticipation of food, which arrives before many 

 minutes have elapsed. In one nest under observation the male de- 

 livered the first food in the form of a small, green insect larva. Dur- 

 ing the first day the male did the major part of the feeding, since the 

 female remained at the nest much of the time to brood the delicate 

 young. She was seen to leave the nest but twice during the first day, 

 probably in search of food- During the first few days the male fre- 

 quently delivered food to the female at the nest, and she in turn fed 

 it to the young. 



By the third day the papillae of the developing feathers of the 

 primaries, secondaries, and tertials, and to a minor degree those of 

 the dorsal tract, have pierced the integument. The remainder of the 

 body remains naked except for the persisting tufts of down. 



On the fourth day the eyes are open for the first time. The response 

 of the young to the presence of the adults is much more marked than 

 during the first days. Both male and female now share about equally 

 in the arduous task of feeding the young, the food still consisting 

 chiefly of insect larvae or soft-bodied adult insects. In feeding, at 

 one nest I had under observation, the adult birds approached the nest 

 silently, except for low twitters. They sneaked through the grass, 

 selecting definite pathways more or less hidden by the vegetation, thus 

 giving an observer little warning of their approach. The female did 



