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 climber 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 cliffs. 







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ta^ ^IBkfete'vsffll !5r™* if 



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Fig. 1. WlIlTE-THROATED SWIFT, 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 case, 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 incubation and possibly 

 save destruction of nests containing eggs that can not be saved in perfect con- 

 dition. 



AVith the exception of that containing set no. 3 all nests were apparently 



