WOODPECKEHS 325 



more, the two sexes bear structural evidence of their equal share in the 

 duty of incubation. During the nesting period the skin on the surface 

 of the abdomen becomes thickened and underlain with a stratum of spongy, 

 vascular tissue, the whole serving to transmit readily the necessary heat 

 from the parent's body to the eggs beneath. 



At Tamarack Flat, on May 26, 1919, a female White-headed Wood- 

 pecker was seen to flush from her nest about ten feet above the ground 

 in a dead pine stub. Tapping by one of us on a nearby bole had caused 

 her to leave, but she returned to the vicinity almost immediately. Then, 

 for fully 25 minutes, while the observer remained within watching dis- 

 tance the bird foraged, preened, and flew about from one to another of 

 the circle of 8 or 10 trees within a 50-foot radius of the nest, but always 

 kept the nest tree in her sight. About every 5 minutes she would fly to the 

 nest. In approaching it, she would swoop below its level and then glide 

 up to the site with decreasing speed so as to end her flight with little or 

 no momentum. Then, having gained claw-hold, she would poke the fore 

 part of her body into the hole, withdraw it at once and repeat this per- 

 formance four or five times before flying away again. Finally, after fully 

 half an hour had elapsed, and her suspicions had been allayed, she went 

 in, to remain. During this entire time the male kept out of sight and was 

 heard only twice. 



On another occasion, following the removal of a set of fresh eggs by 

 chopping out the wall in front of the nest, the observer retired some dis- 

 tance, whereupon the male bird came almost at once to the site. He 

 approached the hole from above and to one side, and upon arriving at 

 the place poked his head into the space which marked the position of the 

 entrance hole ; but he did not enter the wide open cavity. He seemed to 

 be puzzled at the sudden change in the configuration of his home. The 

 next day he or his mate was seen busily digging a new nest in a stub about 

 50 yards distant from the first site. 



Near the east fork of Indian Caiion, above Yosemite Valley, a nest 

 containing young birds was discovered on June 24, 1915. The female 

 parent flushed at our approach and lingered about the vicinity, uttering 

 two kinds of notes at short intervals. The voices of the young could be 

 heard within the nest tree, and upon investigation we found 5 of them, 

 only a day or two old and still entirely naked. They lay on the nest lining 

 of fine splinters and with them were the shells from which they had 

 hatched, each of which had been cut around the middle. 



A White-headed Woodpecker was watched on June 21, 1920, near the 

 village in Yosemite Valley. It was intently searching the trunk of a large 

 Cottonwood and picking naked larvae out from under the bark scales of 



