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 4 THE CONDOR Vol. XIX exact location of the nest within the crevice; it may be to the right, or to the left, or below or above the entrance. By examining the rock formation and looking into the opening one is able to suggest possible locations for the nest, and with all of the available data in mind it is time to start operations. At least two men were required for taking all nests, and, with the excep- tion of set no. 6, they were reached by descending on a rope. It was usually necessary for one man to steady the rope while the elituber was working, espe- cially where overhanging rocks did not permit him to reach the nest on a slack rope. Upon arrival at the cavity the first thing done was to pull up, by means of a small rope, tools for cutting foot-holds, and then, when these had been made, the rocks were removed in such a way as not to crush the nest. As the rocks may vary in size and weight from a few pounds to many tons, and as the exact location of the nest is not known, the man supported by a rope and with scant foot-hold has little in his favor. Set no. 2 and set no. 3 were snatched from the sides of huge falling rocks that were removed from the eliifs. Fig. 1. W][IITE-TI:IROATED SV'IFT, SET NO. 2. All nesting cavities where sets were taken have been completely destroyed in removing the nests. While these operations are under way the birds either remain in the fissures or fly about making an occasional visit to the cavities or to within a few feet of the openings. All nests that I have examined have been infested with numerous "bugs". in the two nests where birds could be seen while incubating, the insects could be observed crawling on the birds' heads. The eggs, in every ease, were more or less spotted as a result of the insects, depending upon how long they had been in the nest. Where eggs can be seen in the nest I believe that observation of the degree of spotted condition will indicate state of ineubatlon and possibly save destruction of nests containing eggs that can not be saved in perfect con- dition. With the exception of that containing set no. 3 all nests were apparently