376 CALIFORNIA ACADEMY OF SCIENCES. 



is Stripped again by a new generation, so that many live- 

 oaks in our surroundings die by exhaustion. 



Phrygaiiidia Calif oi-nica was formerly very rare, and 

 it was not before the year 1859 that I could add the female 

 to my collection. But from that year the Phryganidia 

 constantly has gained ground, which circumstance has to 

 be accounted for chiefly by the decrease in the number 

 of insect-feeding birds. The group of the warblers 

 (Muscicapa) was formerly well represented on the penin- 

 sula and around the bay, but at present most species of 

 these birds have become very rare, some of them being 

 entirely lost to our neighborhood. 



Wherever the small bird is protected, as for instance in 

 the Golden Gate Park, the liveoak is free from the Phry- 

 ganidia and grows well, only being plagued by fungoid 

 growths like the Capnodium, where the groves by too 

 dense growth shut out air and light. 



The introduction of the English sparrow has made mat- 

 ters worse, because the sparrow is himself a very poor in- 

 sect-feeder, but, by pugnaciousness and a certain social 

 organization of his own, he manages to drive away the 

 real insect-feeders, warblers, titmice and swallows, and 

 in this way has become the protector of several of our 

 insect pests. He is a bird of great power T)f adaptation, 

 but of no utility whatever, and in very short time will 

 serve as another living proof how easy it is to disturb 

 the natural relation of things and how difficult to restore it. 



