HEBMIT THEVSHES 603 



mid-day, where the shade is deepest, running along the narrow streets 

 between the tents, just as they do, elsewhere, along the forest aisles. 



In size the Hermit Thrush is about one-third the bulk of a robin. It 

 is slightly smaller than the Russet-backed Thrush, but size alone will 

 not serve readily to distinguish these two. (See pi. 11.) The Hermit has 

 the upper side of the tail from its base strongly tinged with rufous, whereas 

 the Russet-back is of the same brown color over the entire upper surface. 

 Furthermore, the hermit thrush has a notable mannerism of twitching its 

 wings spasmodically every few seconds, a movement often accompanied 

 by a slow downward motion of the tail. These movements serve to identify 

 the bird when it is in the shade where color features are of no avail. 



The hermit thrush population of the Yosemite section is changed 

 entirely each spring and fall. The birds which are present and nest in the 

 region belong to a pale-toned subspecies designated as the Sierra Hermit 

 Thrush. These arrive from the south and are already established by mid- 

 May. Nesting begins soon afterward and the birds depart by the end 

 of August. Then a short period ensues when there are few or no hermit 

 thrushes in the region. By the latter part of September, birds which have 

 nested in various parts of southern Alaska begin to arrive, to spend the 

 winter here. In the fall the Dwarf and Alaska hermit thrushes, as the 

 two races from the north are called, occur in considerable numbers at all 

 altitudes below 9000 feet. The arrival of heavy snow forces most of those 

 in the higher zones to below the 4000 or 3500 foot contour. Our records 

 show the following examples of late tarrying at the higher altitudes. On 

 the snowy morning of December 10, 1914, a hermit thrush was found in 

 a dogwood thicket in Tenaya Caiion one-fourth of a mile above Mirror 

 Lake ; and on December 28 of the same year, 2 were seen at 5250 feet on 

 the Big Oak Flat road near Gentrys. The latter were in thickets of the 

 sticky-berried manzanita (Arctostaphylos mariposa) . 



The demeanor of the hermit thrush is quiet and deliberate. When 

 foraging on the ground it acts in much the same manner as a robin, hopping 

 several times in quick succession and then halting upright and immobile 

 for a few seconds to scan the immediate vicinity before going forward 

 again. There is this important difference, however: the hermit thrush 

 seldom forages out in the open, and if it does it never goes far away from 

 cover, to which it can flee in case of need. Wlien foraging on shaded 

 ground strewn with dead leaves its characteristic performance is to seize 

 a leaf in its bill and throw it to one side with a very quick movement of 

 the head, following this with an intent gaze at the spot uncovered. A 

 thrush will flick over leaf after leaf in this manner, every now and then 

 finding some insect which is swallowed, as is a berrj^, at one gulp. Hermit 

 thrushes thus make use of a source of food not sought after by other birds ; 



