100 PACIFIC COAST AVIFAUNA No. 9 



voices, are equally attractive, and each has its share of birds from late September 

 until the last of them have departed early in April. 



Audubon Warblers share with Say Phoebes the habit of catching flies from 

 a window, sometimes becoming so engrossed in this occupation as to cling for 

 several seconds to the screen where a south- facing window affords a bountiful 

 supply of this kind of food. 



A period of two or three unusually cold nights frequently results dis- 

 astrously for these little warblers, and my observations show that there is a 

 greater mortality among this species than in all other birds combined. After a 

 hard freeze it is not an uncommon occurrence to see certain individuals that 

 appear so benumbed as to be almost unable to fly, and not a few dead birds have 

 been found under trees along the streets. Probably we are safe in assuming that 

 these unfortunates have either been injured at some time, or have become weak- 

 ened through lack of food, and have finally been unable to succeed in the struggle 

 for existence. 



Since the cultivated areas with orchards and vineyards provide a foraging 

 ground that is probably almost as productive as the former wild growths, we 

 may expect the Audubon Warblers to be influenced less by the rapid transforma- 

 tion of the country than almost any other winter visitant. 



Black-throati:d Gray Warble:r. Dendroica nigrescens (Townsend). 



This warbler is given a place among the birds of this district on the authority 

 of Miss Winifred Wear, who mentions seeing a single bird near Fresno, May 15, 

 1907. If this species occurs commonly anywhere in this region, it is during the 

 spring migration ; but as this part of the San Joaquin Valley appears to be not 

 in line with the route followed by most of the migrant warblers, it is probable 

 tliat Dendroica nigrescens appears only as a straggler, and at more or less in- 

 frequent intervals. 



Western Yellowthroat. Geothlypis trichas occidentalis Bicwster. 



This is one of the iiandsomest, and unfortunately one of the siiyest, of the 

 warbler family that occurs in the Fresno district. Unless the observer is familiar 

 with its song the species m.ight remain undetected where it is really quite common. 

 April 6, 191 1, Mr. Grinnell and the author found the Yellowthroats present in 

 some numbers in the rank growth of nettles and young wilkws in the river 

 bottom near Lane's Bridge. Several pairs, probably, were frequenting the tangle 



near camp. 



The distribution of this species over the valley is limited to such tracts as 

 have felt the influence of irrigation ; hence Yellowthroats, like our song sparrows, 

 are found for the most part along canals and in the few natural swampy areas. 

 The flume ponds east of Clovis support a few pairs annually, and each spring I 

 have seen one or two along the Gould ditch. It seems safe to assume, although 

 it has never been proven, that the overflowed areas near Wheatvillc would sup- 

 port nine-tenths of all the Fresno County Yellowthroats. Although the writer 

 has at times searched persistently he has succeeded in finding but one nest, and 

 that one was stumbled upon unexpectedly April 22, 1906, in a willow swamp 

 near Sunnyside. A bunch of tules about eight inches above a pool of slimy 

 water supported the nest, which was in all respects remarkably like the average 



