620 ANIMAL LIFE IN THE YOSEMITE 



The nest found near Lagrange was in a blue oak on a hill top. It 

 was in a naturally rotted-out cavity at a height of 9 feet from the ground. 

 Distant but 17 inches in the same stub was the nest of a Plain Titmouse. 

 The bluebird's nest was 6I/2 inches below the rim of the opening and the 

 sparse lining upon which the 4 eggs lay consisted chiefly of dry foxtail 

 grass. Another nest seen at Smith Creek, east of Coulter ville, was 14 

 feet above the ground in a black oak. A natural cavity about 11 inches 

 deep by 5 inches in diameter had been filled for a depth of 4 to 5 inches 

 with soft materials. Entrance was afforded to the nest on two sides; on 

 the one was a hole about 2i/^ inches in diameter, while there was a much 

 larger opening on the other side, so that the nest was easily visible from 

 without. 



The food of the Western Bluebird, as with most members of the thrush 

 tribe, changes markedly with the season. In summer the birds live chiefly 

 upon insects ; and the young, at least while in the nest, are fed exclusively 

 on this sort of food. But in the colder months of the year, when insects 

 are relatively scarce, the bluebirds, both adult and immature, give their 

 attention to berries. Insects are captured when found, but for the most 

 part the winter food is vegetable in nature. 



The most important single item of food for the bluebirds in the 

 Yosemite region during the winter season is the berry of the mistletoe. 

 (See pi. 13&.) Unfortunate as it may be from the standpoint of the trees 

 parasitized and therefore from the standpoint of foresters and of nature 

 lovers interested in trees, the oaks and certain conifers of the region are 

 rather generally infested with the mistletoe. By reason of the abundance 

 of the berries of the mistletoe, the Yosemite region is capable of, and does, 

 support in winter a bluebird population in excess of that present in sum- 

 mer. This food supply lasts at the higher altitudes until well into the 

 middle of winter, and the birds remain there as an apparent consequence, 

 despite the inclemency of the weather. 



In November and December a large part of the bluebird population of 

 the Valley practically lives in the mistletoe-laden golden oaks along the 

 north wall of the Yosemite. The birds may be found there at any hour 

 of the day and if the observer has the patience to watch an individual 

 or flock of the birds for some time the manner of feeding will be found 

 to be somewhat as follows. 



The birds individually will seek perches about clumps of mistletoe, 

 either on adjacent parts of the tree or on the twigs of the parasite itself. 

 Berries will be picked off and swallowed in rapid succession. Each bird, as 

 it gets its fill of berries, flies to some nearby perch and sits there quietly. 

 The process of digestion is a rapid one, and before many minutes have 

 elapsed enough of the berries will have gone from the bluebird's gullet 



