Giant orioles (_Ostinops_) were also very plentiful, and travelled in large, noisy flocks. One of the more interesting birds was a species of small, red-tailed parrakeet (_Pyrrhura_) which clung to and crawled up the sides of trees like squirrels; it was almost impossible to see them unless they moved, so well did their coloration, and more particularly their actions, conceal them. We had travelled to the Yungas on mules owned by the expedition, and upon our arrival turned them loose to feed as usual. Next morning the animals were in a sorry plight; they had been visited by vampire-bats during the night, and bled so badly that we had to send them back to Locotál without delay. Severe as this attack seemed to be, it was mild compared to what we were to see later on. We discovered clumps of the small bats guilty of the execution spending the days under the roof of our hut, and despatched many of them, but this made no impression whatever upon their vast number. People, also, are bitten on any part of the body which is left exposed at night, and I have frequently seen Indians which had been attacked on nose, forehead, and arms. After completing our work in the Yungas we returned to Cochabamba in order to await more favorable weather for the trip into the lowlands of eastern Bolivia, and to restock our outfit with articles which had been used, and others which it seemed necessary to acquire for the difficult undertaking ahead. After spending several weeks in the vicinity of Cochabamba, we made arrangements with the mail-carrier which enabled us to travel jointly to the Chaparé. He usually made the trip at six weeks’ intervals during the dry season, and, consequently, he knew the trail better than any one else. His _peons_ were also accustomed to the country and knew how to adjust packs so they would meet the varying conditions of the road, which is an “art” that can be learned through long experience only. On July 12 we left Cochabamba. Besides my companion and our personal attendant there were the mail-carrier and his three _peons_; twelve good, strong mules carried the luggage, and there were half a dozen riding and spare animals--quite a cavalcade for the kind of undertaking in hand. Three days after starting we reached our old camping-spot in the Yungas, and, after stopping for a short chat with the old caretaker of Señor Quiroga’s hut we proceeded into what was for us _terra incognita_.