NO. 229S. rpjjj^ GUANO BIRDS OF PERU—COKER. 483 



It well deserves the name by which it has probably been known since 

 prehistoric times: "the guano bird" or guanay. Its gregarious 

 habit, its choice of the level places or more gentle slopes on the tops 

 of the islands for a nesting place, and its custom of remaining on the 

 island a great part of the time, lead to the formation of enormous 

 deposits with very little waste. In the light of the evident adapta- 

 tion of this bird by its habits for the production of large deposits of 

 guano, and in view of the significance of its native Peruvian name of 

 guanay it is difhcult to understand how the chief importance could 

 have been ascribed to any other bird. Nevertheless, the principal 

 credit has been variously assigned by previous observers to other 

 species such as the piquero (gannet) and the penguin. 



The guano of guanays is also found to have a very high value in 

 nitrogen compounds, but whether this is due to the particular char- 

 acter of its food or to other conditions can not be stated. As far as 

 my observations go, the guanay feeds almost exclusively on the an- 

 chobetas or other surface-swimming fishes. In the region where this 

 bird was most abimdant, that of the Chinchas and Ballestas, the 

 cHmatic conditions were most favorable for the preservation of the 

 nitrates. Even though my visits were made during the winter 

 season — ^May, June, and July, when the season of garua (a sort of fog) 

 was prevailing on the coast generally — the atmosphere on these is- 

 lands was invariably clear and dry. It is doubtful if the guano of the 

 Chinoha and Ballestas Islands is ever wet from atmospheric moisture. 

 Consequently the nitrates are not converted into ammonia, to be lost 

 by evaporation or seepage. 



Fourteen to seventeen per cent of nitrogen, or more, may regularly 

 be fomid m the comparatively new guano, and there are many analy- 

 ses of record to show that even the old buried guano of past centuries, 

 when mined from these islands some years ago, yielded as high as 12 

 to 14 per cent, mdicating practically perfect preservation. A sample 

 of new guano which I took in June, 1907, yielded 17.65 per cent nitro- 

 gen T/hen analyzed m September at the sugar experiment station 

 near Lima, through the courtesy of Mr. T. F. Sedgewick. A second 

 sample from the same place kept in Callao, and analyzed in the fol- 

 lowing April by Mr. H. H. Bunting, showed 15.91 per cent nitrogen, 

 while a third portion brought to the United States and analyzed in 

 March, 1909, by the United States Bureau of Chemistry, contained 

 only 8 per cent nitrogen — showing the marked deterioration from the 

 effect of atmospheric conditions. Generally, as the nitrogen is lost in 

 guano, the relative proportion of phosphatic compounds increases, but 

 this means great loss in value, smce phosphatic guanos have little 

 value in comparison with nitrogenous or characteristically " Peruvian " 

 guano. It is due to the rarest chmatic conditions that the millions 

 of tons of guano deposited during the previous times should have 

 retained its nitrogen. 



