NO. 2298. THE OUANO BIRDS OF PERU—COKER. 467 



with reappearing birds; the confused sounds of whirring wings and 

 unremitting splashes. 



The food of the piqueros, as far as I observed it, consisted principally 

 of anchobetas, Engraulis ringens Jenyns; like other sea birds they 

 doubtless feed upon what is most readily available, and they too, 

 doubtless, regale themselves with the small crustacean, Munida coJceri 

 Rathbun, which is sometimes so abundant as to form veritable "red 

 seas" of great area. 



The piqueros seem to prefer the rougher and more inaccessible 

 places for breeding (see pi. 59). Thousands of their nests may 

 be seen upon the face of abrupt cliffs, as at the Chincha Islands; at 

 that particular place they overflowed the cliff, so that a few nests 

 were found on the level ground at the top. This, in fact, was the 

 only place where piquero nests were seen on real table-land. At 

 Guanape (pi. 58) and Lobos de Afuera, many nests were found on 

 very steep and rugged slopes high above the water and approachable 

 only with considerable difficulty. The nests are hollowed, shelflike 

 masses of guano built on some scant ledge, and are usually as closely 

 crowded as circumstances permit. The adult birds readily desert 

 the nests on the approach of an observer, and one must w^ait with 

 some patience for their return. Since the breeding season is continu- 

 ous throughout the year, one may at any time find eggs and all stages 

 of young. The nests contain from 1 to 4 eggs, a considerable pro- 

 portion of them having as many as 3. Nine out of 25 nests counted 

 at one view had 3 eggs. The eggs are a pale blue, smeared more or 

 less with a white, chalky coat, are little pointed and are generally 

 rather uniform in size. The measurements of 5 specimens from the 

 Lobos de Afuera Islands (December 1908) and of 3 from the Chincha 

 Islands (June, 1908) are as foUows: 



Dimensions, in milliTneters, of eggs of Sula variegata. 



Longdiameter 53 61 62 62 61 60 G2 59.0 



Transverse diameter 40 43 43 44 41 42 43 39.6 



The immature birds have the skins of exposed parts of the same 

 color as in the adult except that the tarsus and feet are lighter, in 

 effect a bluish gray. The iris, however, is yellowish gray, instead of 

 clear ruby, as in the adult. The primaries, secondaries, tertiaries, 

 greater and middle coverts, scapulars, and tail feathers, appear before 

 the birds are of full size (pi. 56, fig. 2) . Specimens with the breast and 

 belly feathered, upper tail coverts present, and back feathers appear- 

 ing, show the adult measm-ements. The feathers of the breast and 

 beUy are of light fuscous or gray widely margined with white. The 



