LEAST riBEO 515 



Near Snelling, on May 29, 1915, eig^ht Least Vireos were observed 

 within a stretch of about 300 yards in the low growths beside the Merced 

 River. In an approximately similar extent of stream-side brush along 

 the Tuolumne River southwest of Lagrange, on May 6, 1919, three pairs 

 of these vireos were found. Each pair had a definite forage beat, within 

 which the two birds could be found at almost any hour of the day. 



As regards the niche occupied, the Least Vireo differs from our other 

 vireos in that it chooses a low zone of vegetation in which to search for 

 its food and place its nest. An individual is rarely seen above 6 feet from 

 the ground, and usually it keeps below four feet. Our impression is that 

 all the other vireos habitually forage well above the six-foot level. 



A completed nest of this vireo was found near Lagrange on May 8, 1919. 

 (See pi. 51a.) It was in deep shade under a thicket of willows and white 

 alders which grew on the lower slope of a pile of gravel left by a gold 

 dredger. The nest was 19 inches above the gravel, and instead of being 

 placed in one of the stout crotches of the adjacent alder it had been lashed 

 to a slender fork on the brittle stem of a weed of the previous season's 

 growth. This was only 7 feet from the margin of a pool of quiet water. 

 In form the nest was a well rounded, deep and rather thin-walled cup 

 with slightly inrolled rim. It was composed of dry shreds of plants felted 

 compactly with down from cottonwoods and willows. Outside, it measured 

 2 inches in height and 2i/2 inches in greatest diameter, while the interior 

 was 11/^ inches deep at the center and about 1% inches across the opening. 



When first found, this nest was empty, but on the following day, by 

 6 :30 A.M., one egg had been laid. During our second examination of the 

 nest the male came close and sang his song at intervals of 10 or 15 seconds. 

 To one observer the song sounded like this: we-cher, cJte we, eke we-cheyf 

 we clier, che we, eke we, ckeey! Each set of syllables was uttered rapidly, 

 with a distinct rest between the two. 



Another pair of these little vireos was watched around one of the other 

 small ponds in the same general locality. The female was foraging and 

 she moved about rather rapidly, occasionally flying upward a short distance 

 to get some particular insect on the leafage. Meanwhile the male traveled 

 along with less frequent change of position, keeping to perches fairly close 

 to his mate, and singing at short intervals. When he was giving the song, 

 his whole body vibrated with the effort, the throat swelling visibly at each 

 syllable, and the tail being depressed at the same time. This song was 

 transcribed on the spot as wreteky, wreteky, wretcky, wretcky, wreef 

 wretcliy, wretcky, wretchy, wretckenr, wreer. The r's here indicate a 

 burred or rolling quality ; and the whole song was, as usual, hurried in its 

 delivery. The question-and-answer inflection was striking. 



