206 
THE CONDOR 
Vol. XIII 
cleared away and the weeds allowed to grow, Brewer sparrow’s were exceedingly 
common. 
During an early morning walk through brush and forest the following birds 
were seen: blue-fronted jay, Brewer sparrow, green-tailed tow’hee, western house 
wren, bush-tit, Calaveras w'arbler, w’estern robin, red-shafted flicker, and Lewis 
w’oodpecker. Within the space of three-quarters of an hour, five different species 
of birds were seen to perch in a dead cedar on a small hill. The tree was first 
visited by a Bullock oriole, then by a small flock of western bluebirds, four other 
Bullock orioles, tw’o cliff swallows, which perched on the topmost limb, several 
purple finches and an evening grosbeak. 
In a little meadow west of Sisson, where grass and weeds grew in abundance, 
a large number of birds w’ere seen. In the weeds green-backed goldfinches and 
Brewer sparrows were feeding iti large flocks. Several flickers were feeding on the 
ground. A lazuli bunting flew into a fir tree where several Calaveras warblers 
were at work. A sparrow was heard in a nearby tree. Several robins flew from 
one tree to another. A western bluebird was perched on a stump. 
With the plague-ridden territory inhabited by so large a number of species of 
birds and by so large a bird population, it may at first seem strange that only five 
species of birds were found to feed on Eugoiiia californica. The investigation 
showed that only the larger birds fed on the butterfly. Certainly most of the 
small birds are ill-adapted for catching insects as large as the butterfly in question. 
Their most intimate relation to the outbreak was doubtless when the insect was in 
the larval and pupal stage. If all the birds smaller than the Say phoebe be elim- 
inated from the list as being unable to act as checks on the butterfly, we find that 
over twenty-two percent of the species of the larger birds fed upon the butterfl}’. 
If we eliminate those of the larger birds, which judging from their food habits 
would not feed upon the butterfly, we find that almost forty percent of the possi- 
ble species did feed upon the insect. 
A striking fact is that the birds acting as checks, with one exception, that of 
the Say phoebe, are birds about whose depredations there is considerable complaint 
by the farmers of the state. That the blackbird, meadowlark, jay, and kingbird 
all do a certain amount of harm is undeniable, but too often only one side of the 
question is emphasized. 
Especial attention is called to the fact that even such a bird as the blackbird, 
which is often classed as the worst pest of the farmer, may become of value at 
times and places where it is least expected. The present paper shows that the 
same birds that are often classed as harmful may be very beneficial in the checking 
of an insect outbreak. 
Even though the brush attacked by the larva of Eugonia californica is seldom 
killed by the defoliation, yet the plants must be weakened to some extent. If the 
economic value of the brush be measured by its use as forage for deer and sheep, 
it will be seen that some importance, at least, attaches to this particular insect out- 
break in that the defoliation took place during the summer when it was most 
needed as forage. The economic importance or non-importance of the outbreak, 
however, in no way affects the value of the principle involved in the relation of the 
birds to the epidemic; namely, that birds prey upon the insect food most abundant 
and therefore become factors in the checking of an insect outbreak. 
In the life history of such an insect as Eugonia californica , we find the maxi- 
mum number of individuals soon after hatching begins in the spring. From this 
time on there is normally a rapid decrease in numbers. The decrease is due to, 
not only the action of birds, which are perhaps the most constant factor in the de- 
