Mar., 1918 THE SALT MARSH YELLOWTHROATS OF SAN FRANCISCO 63 



densed form of two syllables ; but the power of it rises rapidly as the year ad- 

 vances until by the end of March its nuptial gladness pours forth in full-throated 

 volume. Sometimes as evening approaches, one of the little black-faced birds 

 will leap into the air with fluttering wings and expanded tail and as it slowly 

 tumbles down into the grass again, will execute an exquisite series of melodious 

 runs and trills not unlike the vocal accomplishments of the Chat. 



The nesting period ranges from middle April until June, fresh eggs having 

 been taken on April 2 and June 18. The yellowthroats, habitually suspicious, be- 

 come doubly vigilant during the breeding season and I think that only twice in 

 all the years I have studied them have I surprised the female in the act of carry- 

 ing nesting material. It has been my experience that if an unfinished structure 

 not containing eggs is located, the birds promptly abandon it. The nest, a cup- 

 shaped, fairly compact receptacle is usually composed of lengths of dried grass 

 well interwoven with the supporting stems. It is commonly hidden in bunches of 

 wire grass or weeds among willows and jjlaced from six to twenty-four inches 

 above the ground. The bowl-like interior is often lined in rather a loose manner 

 with dried grass or thin fiber. The usual complement is four though a set of 

 three, particularly when laid late in the season, is not rare. The eggs are taper- 

 ingly oval in shape, white, with a decided pink tinge when fresh, and circularly 

 splotched about the larger end with^dots and dashes of black, brown, and deep 

 lavender, varying in size from minute markings on some specimens to a pro- 

 nounced ring of color on others. Incubation, which is performed by the female, 

 usually occupies about fourteen days. 



There has occurred of recent years a serious factor which may possibly, if 

 long continued, result in permanent changes in the nest-building of these birds. 

 It has become a custom of the Italian truck gardeners who cultivate the upper 

 hills of Merced to make frequent excursions down to the lakes to cut the tough 

 wire grass in which sinuosa nests, in order to use it for binding vegetables, thus 

 economizing in cord. For this purpose the grass is collected in enormous quan- 

 tities, great swathes being opened through the thickest growths and in other 

 places entire meadows being utterly denuded. As this destruction takes place 

 during the time when eggs and young are in the nests, it is reasonable to conclude 

 that numbers of these are annually destroyed. It has lately appeared to Mr. H. 

 W. Carriger (and my observations w^ould tend to confirm his conjecture), that 

 as a result of this persecution the yellowthroats are nesting less abundantly in 

 the grassy flats and adapting themselves more to life in the inaccessible tules of 

 the open lake, or else building their homes higher up toward the banks amid 

 thickets of blackberry and willow. Certainly the number of sets found in these 

 localities is far greater now than in former years, and in time such safety zones 

 may be used exclusively. 



While incubating, the females often show remarkable shyness in slipping off 

 the nest and keeping well ahead of the observer, with short undulating flight. 

 Occasionally as evening approaches they are apt to flush from directly beneath 

 one's feet, particularly should he beat Quietly up toward them against the wind. 

 When startled from her nest the female disappears and maintains silence for 

 some moments but if the intruder remains in the vicinity, or removes the nest or 

 eggs, her sharp chack of alarm will rapidly summon the male and the pair will 

 flit nervously about in the underbrush, often fearlessly approaching within a few 

 yards of the observer. 



