474 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 56. 



The distinctive features of tlie two Peruvian species of Sula are 

 indicated by the following comparison: 



S. variegata. 



S. nebouxi. 



Measurements ' 



Iris ! Ruby 



Foot and tarsus ... ! Dull blue. 

 Head and neck } Shining white. 



10 to 20 per cent greater. 

 Pale yellow. 

 Brighter sky blue. 



Brown spotted and streaked with white. 

 Nests on the level ground or gentle slopes, widely 

 scattered, along with nests of gaviotas. Bold 



Breeding habit. . . Nests on roughest places or on 



j cliffs, as closely aggregated as 



I possible. in defending young. 



Habit, general j Clannish— not often seen at rest | Spends much time on the islands, resting on the 



except St the rookery. rocks of the shores or on the hillsides, frequently 



with the pelicans. 



THE CORMORANTS. 



The three species of cormorant of the Peruvian coast are, as will 

 be seen, conspicuously distinct in plumage and in habit. The mem- 

 bers of each species are numerous, but only one is of great signifi- 

 cance economically. This is the "guanay" (P. hougainvillei) , the 

 most important guano producing bird of the coast. Strangely 

 enough, this species is a less familiar one than either of the other two, 

 although exceeding either of them in abundance. One may not visit 

 a pier without hearing the grunts of the "cuervo de mar" (P. vigua); 

 one may hardly take the shortest trip on the water without seeing 

 the scarlet-footed "patillo" ("little duck," P. gaimardi) scurrying 

 low over the water; but one may be ignorant of the most abundant 

 species, unless by chance his boat pass near a cloud comprising per- 

 haps hundreds of thousands of the "guanays," or, unless the solid 

 black crest of some islet be pointed out as a rookery of "guanays." 



PHALACROCORAX BOUGAINVILLEI (Lesson). 

 THE WHITE-BREAST CORMORANT, OR "GUANAY." 



It need not be inferred from the previous remarks that the guanays 

 occur invariably in enormous aggregations, for there are many rela- 

 tively small rookeries. A flock of considerable size was noted at the 

 Lobos de Tierra Islands, crowning an islet off the west side of the 

 northern portion of the main island. A "loberia," or rookery of sea 

 lions, bordered the lower portion of the island. Several birds were 

 seen also at the Lobos de Afuera Islands, where no rookery was ob- 

 served. Smaller rookeries were found at the Pachacamac Islands and 

 Asia. 



The preeminent home of the guanays, at least in 1907 and 1908, 

 was the double group of islands off Pisco in the south, the Ballestas 

 and the Chincha Islands (pis. 61 and 62). Each of the two island 

 groups, which are only 5 nautical miles apart, comprises three prin- 

 cipal units, those of Ballestas, the southerly group, being much 

 smaller and much higher than the Chinchas. In each case we have 



