364 ANIMAL LIFE IN THE YO SEMITE 



Olive-sided Flycatcher. Nuttallornis borealis (Swainson) 



Field characters. — Smaller than Robin but large for a flycatcher. Head big and tail 

 short as compared with other flycatchers. Middle of lower surface of body from chin 

 backward yellowish white; plumage elsewhere solid olive brown save for patch of 

 white on flank. Perches at tops of tall coniferous trees whence it flies out in tj'pical 

 flycatcher manner after passing insects. Voice: Song a loud clear far-carrying wher, 

 whee', whew; call notes a softer pnck, twice or thrice repeated, most often heard in 

 evening. 



Occurrence. — Moderately common summer visitant to Transition and Canadian zones 

 on west slope of Sierra Nevada. Passes through lower zones on both slopes during at 

 least the spring migration. In Yosemite Valley, at least in early summer, but not 

 plentiful there. Arrives in nesting range from middle of May to early June and departs 

 about the end of August. Solitary or in pairs. 



The Olive-sided Flycatcher is the patrician among the flycatchers, as 

 it arrives late in the season and departs early, and while here maintains 

 itself in seclusion from most other birds by keeping to the tops of the 

 tallest trees. It spends the winter months in Central America or northern 

 South America and so is a far traveler during its absence from our 

 mountains. During late May and early June birds of this species are 

 to be heard or seen, from time to time, in the foothill country where they 

 pause to rest and feed before resuming the journey to the forests they 

 quitted the previous summer. 



At Blacks Creek west of Coulterville, on May 11 and 12, 1919, Olive- 

 sided Flycatchers were moving past our camp on their return to the 

 mountains. One was seen to perch momentarily on a convenient power 

 wire over a greasewood-covered hillside before going on in a northeasterly 

 direction toward the adjacent mountains; another heard calling from a 

 solitary digger pine in the early morning was gone when looked for a 

 little later. At Pleasant Valley, on May 23, 1915, individuals were observed 

 in similar leisurely movement, going toward the cooler pine forests not 

 many miles distant. At Mono Lake Post Office the species first appeared 

 in migration in 1916 on May 22. The latest fall record is for September 1, 

 1915, when two birds were seen in Jeffrey pines at the head of Sunrise 

 Creek, near Clouds Rest. 



The Olive-sided Flycatcher is one of the earliest birds to call in the 

 morning and one of the last to be heard in the evening. This is probably 

 due in some degree to its choice of surroundings, for in the tree tops it 

 is apprized of the coming of dawn long before that news reaches the 

 earthward dwelling species, and in the same places it enjoys the lingering 

 daylight for some time after the glades and thickets below are lost in 

 the shadows of the evening. At Chinquapin on June 17, 1915, where 

 these birds were already located for the summer, the clear three-syllabled 



