322 ANIMAL LIFE IX THE YO SEMITE 



approach to a dead stub near the east fork of Indian Caiion, disclosed the 

 location of her nest. In May, 1919, when especial attention was paid to 

 the nesting habits of birds, 9 occupied nests of this woodpecker were 

 discovered. Three of these were found at Hazel Green on May 14 and 15, 

 and 6 near Tamarack Flat May 2-4 to 26. 



Of the 10 nests concerning which we have data, the lowest was located 

 only 58 inches (measured) above ground and the highest, 15 feet (esti- 

 mated). A nest of the Mountain Chickadee occupying what was evidently 

 an old nest of this woodpecker was but 50 inches above the ground. Prob- 

 ably 7 feet would be the average height at which the nests of this species 

 of woodpecker are placed. Dead stubs, either cut or broken off, seem to 

 be the preferred sites for nest holes, for by far the greater number of 

 nests were in such stubs. 



No nest holes of this woodpecker Avere found in living conifers. Nor, 

 on the other hand, do the birds seek what is commonly known as rotten 

 wood, that is, wood too soft for the nest cavity to be maintained against 

 the incessant wear involved in the birds' passage back and forth, incident 

 to the rearing of a brood. The tree chosen must have been dead a sufficient 

 length of time for the pitch to have hardened or to have descended to the 

 base of the tree, and the outer shell of the tree must still be hard and firm, 

 whereas the interior must have been softened to a moderate degree bj?^ decay. 

 These conditions are not to be met with in every standing dead stub ; hence 

 the choice of a nest site becomes a matter of rather fine discrimination. 



As evidence that considerable investigation by these birds precedes the 

 excavation of the nesting hole finally occupied, we found many ' prospects, ' 

 varying from shallow pits, conical in form, where a woodpecker had begun 

 excavation only to leave off without even penetrating the outer hard shell 

 of the tree, to those where a bird had entirely completed the laterally 

 directed tunnel into the softer wood within, but had not sunk the shaft 

 which forms the nesting cavity proper. Often we found numerous fresh 

 prospects on the same bole, and sometimes these were close to a newly 

 completed and occupied nest cavity. We were led to conclude from all 

 this that the White-headed Woodpecker is either notional or else very 

 particular, in the selection of its home. Evidence points strongly to the 

 birds excavating and occupying a new cavity each year, although one set 

 of eggs was found in a hole which had been dug in earlier years. 



Some stubs are literally riddled with holes, these probably recording 

 successive years of occupancy. One stub had at least 5 fully excavated 

 holes besides 11 or more prospects. Hence it will be seen that the activities 

 of these and other woodpeckers contribute rather directly toward bringing 

 down the standing dead timber. Drilling by woodpeckers results in an 

 increase in the number of entrances through which insects may get at the 



