1024 U.S. NATIONAL MUSEUM BULLETIN 23 7 paet 2 



ical periods of laying and hatching would be necessary to measure 

 the incubation period with greater precision. 



Young. — In the nest I watched in 1956 the young hatched some 

 time after 9:30 a.m., June 16, and before 5:00 a.m., June 19. When 

 I visited the nest on June 19, the young were very small and black- 

 skinned with some gray down. They held their heads straight up, 

 begging for food, and one gaped as I leaned over the nest. On June 

 21 they gaped in response to my tapping the edge of the nest, but 

 not to my blowing on them or shading them with my hand. At 

 that time they showed down on top of their heads and the feather 

 tracts on wings and bodies were appearing. 



On June 23 I arrived at the nest at 6 :00 a.m. and tapped the edge 

 of the nest. The young closest to me responded by gaping but 

 the others did not, and I presumed that they had just been fed. 

 Thirty minutes later, during which time they were not fed, tapping 

 the nest produced an immediate gaping response in all four young. 



On June 24, 1956, I banded and weighed the young and collected 

 the following data (weights in grams) : 



When I replaced them in the nest, they aU gaped at me, pushing 

 so hard that I had trouble finding room for the last one. At this 

 age their wing and tail feathers are beginning to break through the 

 sheaths. 



After being weighed on June 25, all the young were able to scram- 

 ble back into the nest. They then had a single distinctive call note 

 unlike that of the adults. The wing and tail feathers were well 

 developed by that time, but the white wing bars were not yet evident. 



The young left the nest between 6:00 p.m., June 26, and 9:00 a.m., 

 June 27. On the latter day two of the young, still flightless, were 

 found in the vicinity of the nest. One was hiding in a clump of 

 grass, and one under a yucca. On subsequent visits to the nest 

 during the next few days I was unable to find any of the family. 



Dennis Carter reports (in litt.) the following observations from 

 Jewel Cave National Monument, Custer County South Dakota, in 

 1958. "White-winged junco is one of the most numerous species 

 here and, on July 1, I found a pair with young birds. The adults 

 were very agitated by my presence and uttered sharp alarm notes. 

 When I finally discovered a juvenile bird, one of the adults swooped 

 down over my head. I found three young birds, and although they 



