512 ANIMAL LIFE IN THE TOSEMITE 



year 1915. Mr, Joseph Mailliard (1918, p. 19) states that a few were still 

 in Yosemite Valley on September 28, 1917. 



The Cassin Vireo is the largest of the four species of vireos in the 

 Yosemite section. (See pi. 50.) In general, the bird gives the impression 

 of having an abnormally large head and short tail, and of being big-eyed, 

 the latter obviously by reason of the conspicuous circlet of white around 

 the eye. In good light the head appears an olive slate, the back greenish, 

 and the under surface ashy white, with a yellowish tinge on the sides. 



The movements of this vireo are like those of the Warbling Vireo, but 

 they are even more slow and deliberate. It perches stolidly, and when 

 insects are spied captures them by direct thrusts of the bill. Occasionally 

 a bird will poise on fluttering wings to seize some object not otherwise 

 obtainable. But even then, there is little suggestion of the nervous activity 

 of, for example, the Audubon Warbler. 



The Cassin Vireo is a slow but persistent singer ; the syllables of its 

 song are set off from one another by long rests. With one bird which was 

 kept under observation for some time these breaks varied from about one 

 to ten seconds. Another, similarly studied, sang at intervals which, by the 

 watch, ranged from one to three seconds. After a long series of these 

 closely spaced notes the latter bird was quiet for ten minutes or more save 

 for two series of five or six notes each. Each note is clear cut and loud 

 so that the song rings out, and may be heard for a considerable distance. 

 Successive notes are variously inflected, some rising, others falling; at 

 times a bird will give a regular alternation of rising and falling inflections. 

 Hence the name " question-and-answer bird" has been suggested for the 

 Cassin Vireo. Some of the notes were syllabified by one of us as tseer', 

 pee'rit, pee'-o-wiip, syrup, que'-up, tseer, etc. Another series was written 

 as clie'weh, cheweuh' , ohe wer, occasionally wee'chd. The notes suggest 

 the words ' ' to eat ? to cheer ! ' ' The bird has also a scolding or alarm note 

 che, che, che, and the two members of a pair when together may indulge 

 in low conversational notes. The Cassin Vireo continues in song through 

 much of the summer, one in song being heard in Yosemite Valley on 

 July 23, 1915. There is a revival of song after the molt ; on September 2, 

 1915, one was heard in the Valley giving a song almost as full and per- 

 sistent as that ordinarily to be heard in the spring. 



A nest of the Cassin Vireo was found in Yosemite Valley on May 22, 

 1919. It was placed in an incense cedar at the edge of the Merced River. 

 The nest was on a branch which extended out over the rushing stream 

 and was about 18 feet above the surface of the water. The nest was a 

 deep cup lashed by the rim to two forking branchlets forming a crotch. 

 The following day another nest, in an early stage of construction, was 

 found near the road along the north side of the Valley. It was TVo feet 



