Mar., 1917 



LIST OF BIRDS BREEDING IN SAN FRANCISCO COUNTY 



55 



ty. Although the county is small it presents some points of marked ornitholo- 

 gical interest. 



The Farallon Islands furnish a nesting place for thousands of birds from 

 the open sea, and in the nesting season these rocky islets present one of the 

 most striking ornithological phenomena to be seen in any of the states of our 

 Union. The mainland portion of the county is not without interest to the 

 thoughtful student of birds. There is probably no area of similar size in the 

 State which has so much to teach us concerning the effects of human environ- 

 ment on bird life. 



Vast changes have taken place in this little area during the last sixty 

 years. During that time a city of a half -million people has grown up on the tip 

 of the peninsula south of the Golden Gate. Salt marshes have been filled, and 

 the shore line in many places pushed far out into the bay. Hills have been 

 leveled and creeks filled. Bushy hillsides and sand-dune tracts have been built 



Fig. 20. Stow Lake, in Goldex Gate Park, Sax Fraxctsco. 



up into residence districts. Such changes must of necessity affect the avifauna 

 of a region. 



Indeed, at first thought, one might wonder whether many species of birds 

 would remain after such sweeping changes. That many species have not only 

 survived but have actually increased in numbers, and that several new species 

 have come to make their homes in the county, is the conclusion toward which 

 the present avifaunal condition of the county seems to point. 



In undertaking this study of the nesting birds of San Francisco County 

 we have had two objects in view. Our first object has been to furnish to those 

 interested in our birds a reliable list of species making this county their home ; 

 for a bird's home is where it builds its nest. Our second object has been to fur- 

 nish, if possible, some reliable data concerning that far vaster problem, namely, 

 the effect of the occupation of a territory by the white race upon the native 

 birds. In order to furnish data of the last named kind we sought to learn as 



