324 ANIMAL LIFE IN THE YOSEMITE 



Two of the nest cavities we found were in such unusual sites as to call 

 forth comment. One at Hazel Green was in a slantingly upright limb on 

 a prostrate dead black oak trunk lying in a grassy meadow, fully 150 feet 

 from the margin of the forest. The hole was excavated on the lower side 

 of the stub. The other nest was at Tamarack Flat, in the butt end of an 

 old log, lifted above the ground when the tree fell over a granite outcrop. 

 This hole was about 7i/^ feet above the ground, and as with the other there 

 were piles of chips immediately beneath it. 



We were unable to conclude that the nest holes are located with any 

 special regard to direction of exposure to the sun or weather. There 

 seemed to be no rule as to their position with relation to the cardinal 

 points. Probably the availability of appropriate surfaces in which to 

 excavate is much more important in the choice of a site than is the possible 

 protection from the elements. 



In one stub was found a nest hole excavated in some previous year, 

 but again occupied for the current season. This same barkless stub showed 

 four weathered prospects. About the margin of the entrance to this nest 

 were many claw marks, which aggregated into trapezoidal patterns, register- 

 ing the positions of the toes, two up and two down. The tracks were most 

 numerous immediately above the nest, showing that it was the custom 

 of the woodpeckers, when going to the nest, to alight above the hole in the 

 spot indicated and then back down to the entrance. 



Eggs of the White-headed Woodpecker are typical of w^oodpeckers in 

 general, in that they have a white, shiny surface entirely lacking any 

 natural color markings — "immaculate" in the vernacular of the oologist. 

 The eggs in one set had a wrinkled appearance at the smaller end as though 

 that end had been compressed before the shells had hardened. Eggs which 

 are advanced in incubation are apt to be soiled by pitch; this is doubtless 

 brought in by the parent birds on their bills, feet, or plumage. The eggs 

 always rest on a lining of fine chips or rotten wood, and the nest, even 

 after the young are hatched, is maintained in a marked state of cleanliness. 



A set of 4 fresh eggs collected at Hazel Green on May 14, 1919, weighed 

 20.5 grams, and a set of 5 fresh eggs taken the next day weighed 25.3 

 grams; while a set of 5, 4 of which were advanced in incubation, taken 

 on the 14th, weighed only 20.7 grams. It is thus evident that these eggs 

 lose considerably (15 to 20%) in weight as incubation advances. 



We did not arrive within the range of the White-headed Woodpecker 

 early enough in any year to ascertain whether or not both sexes assist in 

 excavating the nest cavity. But after the eggs are laid, the male and 

 female share alike in the duty of incubation. Ftom the same nest hole we 

 have in turn flushed the female and then the male ; and in other instances 

 birds of one sex or the other were flushed, in about equal ratio. Further- 



