MOUNTAIN BLVEBIBD 625 



insects which pass by. For insects which live on the ground, such as 

 grasshoppers, the bird mounts 10 to 20 feet into the air over the grass- 

 land and then by fluttering its wings rapidly, hovers in one place for several 

 seconds and intently scans the surface below, like a Sparrow Hawk when 

 similarly engaged. If something is sighted the bird drops quickly to the 

 ground and seizes it; otherwise the bluebird moves a short distance to a 

 new location which is given similar scrutiny. It thus examines the ground 

 in a manner recalling that employed by the robin though from an aerial 

 location where its scope of view is much greater though less thorough. 

 The Mountain Bluebird elsewhere in its range is known to eat berries 

 though not to the extent of its lowland relative; none of the birds which 

 we saw or collected in the Yosemite section gave any indication of having 

 eaten food other than insects. 



