NO. 2298. THE GUANO BIRDS OF PEBU—COKER. 469 



the water below, and that even entire nests will break away when 

 too heavy and drop into the sea (pi. 59) In some cases, a small 

 beach below may serve to collect the falhns; guano and keep it avail- 

 able for extraction. 



It is not thought to be by any means physically impracticable to 

 build shelves at the base of cliffs or to contrive other means for con- 

 serving the waste guano from the nests in such places. This will not 

 be done, however, so long as the extraction of guano at any par- 

 ticular situation is subject to lease to any one of several competitors. 

 The contractor who would incur large initial expense for construction 

 of such equipment must be assured, not only of his own exclusive 

 privilege of taking the guano from such situation, but also of his 

 license and power to protect his property from depredation or dam- 

 ages. Von Tschudi found that a single Sula variegata (piquero) in 

 captivity would produce 3^ to 5 ounces of guano a day. (See his 

 Travels, p. 169.) Supposing 1 ounce of this to be deposited at 

 the island each day (a low estimate), it is evident that a thousand 

 piqueros would produce 365,000 ounces a year, or 11^% tons a year — 

 or a million birds 11,400 tons, say, practically half a million dollars' 

 worth. The numbers of Sulas on the Peruvian coast and islands 

 would far exceed the million. The piqueros, therefore, offer one of 

 the best opportunities for hope of increase in the amount of extract- 

 ive guano. 



One of the illustrations shows a chff at the Chincha Islands on 

 which there were at least 1,000 nests. Guano to the amount of many 

 tons is formed at such a place each year but is almost entirely wasted 

 by falling into the sea. 



It has been mentioned, too, that in this case, at the Chincha 

 Islands, a few piqueros were found to have their nests on the table 

 lands beyond the top of the cHff . It is not impossible that, were the 

 islands less frequented and the bird quite undisturbed, a larger pro- 

 portion would frequent the level ground where the guano of ^,he nests 

 would be entirely preserved. This appears to have been the case in 

 the time of Raimondi.^ 



While the Sula variegata occurs along almost the entire coast of 

 Peru, it is more especially a bird of the southern region. Very abun- 

 dant as far north as the Guanape Islands, it is less conspicuous there; 

 there is, however, a considerable rookery at the Lobos de Afuera 

 Islands still farther north. A little farther north, at Lobos de Tierra, 

 this species is far less numerous; the other and larger species of Sula, 



' Raimondi, A. M6moire sur le huano des Isles de Chincha et ies oiseaux qui le produisent. Comp. rend. 

 Acad. Sci., vol. 42. Paris, 1856. 



Raimondi, Antonio. El Peru— estudios mineralogicos y geologicos. (Ser. 1.) Volumes 1-4. Publicado 

 por la Sociedad Geographica de Lima 1874-1902. Article entitled: Apuntos sobre el huano y sobre las 

 aves que lo producen. In volume 4, 1902, pp. 489-496. This article is evidently based upon the earlier 

 paper just cited, but seems to represent a revision . 



