ttO 



PACIFIC COAST AVIFAUNA 



No. 9 



I have observed nests built up to a height of four or five inches and placed 

 on hard dry ground, and have seen others that were sunken in an excavation so 

 deep that the female bird on the nest was hardly visible. Probably seven out of 

 every ten in this part of the valley are well hidden on the ground, at the base of 

 a vine in a vineyard. 



The nests are usually well made, there being a substantial outer structure of 

 dry weed stems, grass and rootlets, lined, almost without exception, with long 

 black horsehairs. 



In my experience the Lark Sparrows are quick to resent any molestation of 

 their home, not infrequently deserting, even when the nest is noi touched ; but 

 the following incident will show that such is not always the case. Late in April, 

 1907, a nest was found with one fresh egg. Two days later I visited the place and 

 could not find either of the owners, nor could I account for one of the eggs being 

 on the ground fully eight inches from the nest while the other two were just 

 outside and resting on the edge of the nest material. The horsehair lining was 

 undisturbed so I replaced the three eggs. The following day one of the birds 

 was occupying the nest again, and had added another egg to the set. 



In one case that came under my observation the eggs hatched on May 4, and 

 the last young bird left the nest on the 15th. It is interesting to note that the 

 elongated type of eggs that are occasionally met with, resemble in size, shape 

 and markings, certam specimens produced by the Bullock Oriole, although the 

 usually almost spherical eggs of the Western Lark Sparrow can be distinguished 

 at a glance from those of any other bird. 



The following table will show the nesting dates recorded by the author in the 

 past ten years: 



Incubation 



well begun 



somewhat advanced 



fresh 



slight 



well begun 



commenced 



begun 



advanced 



5 or 6 days 



slight 



fresh 



fresh 



advanced 



begun 



advanced 



begun 



begun 



advanced 



begun 



very slight 



begun 



