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Sept., Some time before I had found a nest of young Snowbirds, and on the 5th I visited them for the last time to see them take their initial flight. It was a fine day and I was soon rewarded for n-aking the trip, the birds leaving their nest quickly after the first one led the way. For awhile it was all riglit, but soon two became entangled in the long grass near the nest and in a minute there was quite a commotion. After awhile one flew out but he was no sooner out than he was pounced upon by a medium-sized chipmunk that had followed him and I at once knew what had caused the commotion. The chip- munk was as quick as a cat, and by the time I got there and drove him off, the bird was dead. I hunted around quite a while for the other one but was unsuc- cessful, so I watched the two tenmining ones until they were safe. One week later almost' the same occurrence was repeated about five miles away, but in this case I managed to lay the chipmunk out for good, while be in turn only killed one of the young Snowbirds. On July i6, the last piece of evidence was seen by me, when two young I,ouisiana Tanagers were thrown from their nest suddenly during a struggle that occur- red between one of the parent birds and a medium-sized chipmunk. The latter was bent on mischief and the young ones either were frightened out of the nest while the male hird attacked the animal, or else fell out accidentally. It also showed me a new trait in the character of the adult bird. On July 27 I noticed several chipmunks heing driven away from some tamarack trees on the lake shore, by a band of Motln- tain Chickadees. Later on I found that a pair of these birds had a nest in one of the trees, and I presume that when they found the chipmunks were bent on mischief, they summoned their mates to help them, as they and the flycatch- ers often do. My summer's notes contain no ntore direct evidence against them, but natur- ally, after a close study of the habits of THE CONDOR 99 these aninmls and their results to the lives of our young birds, I have arrived at certain conclusions in regard to them which I give as being pertinent to this article. To begin with, the few in- stances that I have come across in a summer's work of destruction done by chipmunks to birds, would undoubtedly be greatly multiplied if systematic atten- tion was paid to their wrong-doings by a larger number of observers, so there would then be no doubt as to their being to blame for a considerable per- centage of the scarcity of mountain birds. In thus laying part of the blame on the_ chipmunks, we unconsciously give them some competitive advantage over the birds of their own habitat, or else we must grant that the agencies of man interfere in some way to their good, for were it not so their relative numbers would remain the same and nature's balance would continue undis- turbed. After studying them closely for a long time, I have been unable to see where any agency of nian interferes advantagously to the chipmunks, for the small amount of food they derive from us, is in itself insufficient to account for their increase in numbers over the birds; our presence affords them no better protection from their enemies or from climatic conditions, and in no other way can I make out that nlan or his agencies work to their advantage. Therefore in allowing that they possess some competitive advan- tage over the birds of their own habitat, with whom they enter into severe coin- petition during the active portion of their lives, I have heen led to coinpare in detail their habits, one by one, with similar features of the birds of the vicinity, in order to find out what was the nature of this advantage, and I con- sider that it is directly due to the much more varied food supply of the chip- munk. Indirectly too, the limiting and ab- sence of great variation of the supply of birds, decreases the extent of their range and confines them to special