THAYER AND BANGS: VERTEBRATA OF GORGONA ISLAND. 93 



the new bird the forward part of the head only is gray, shading into the 

 dark sooty brown of the rest of upper parts at nape, on cheeks and on throat 

 just below the gular sack (in /S. breusteri the adult ^ has the head entirely 

 whitish and the neck ashy gray shading into color of back at shoulders). The 

 female of the new form has the whole head and neck, dark sooty brown con- 

 color with the back, like Sula leucogastra (the female of S. brewsteri has the 

 head and neck distinctly lighter or grayer than the back). Young as well as 

 adult examples are darker brown than specimens of >S'. hrewsteri in corre- 

 sponding plumage. 



Colors of Naked Parts in Life. — Adult ^ : Bill dusky, slightly yellowish 

 toward base; gular region and skin around eye dusky, sometimes tinged with 

 greenish yellow; tarsus and foot pea-green. Adult 9 • Bill, gular region, skin 

 around eye, tarsus, and foot sulphur yellow. 



Measurements — 



Locality. 

 Gorgona Isl. 

 Saboga Isl. 

 San Miguel Isl. 

 Gorgona Isl. 



do. 

 Saboga Isl. 



Geographic Distribution. — Sula etesiaca is not confined to Gorgona Island, but 

 breeds also in great numbers on Saboga Island, — the '• bird rock " of the Pearl 

 Islands in the Bay of Panama, — Mr. Brown securing a large series on the 

 present trip at the last-named place. Cocos Island, between Panama and the 

 Galapagos, is another breeding place, Mr. Nels(m informing us that specimens 

 in the National Museum from this island are identical with ours from Gorgona 

 and the Pearl Islands. 



Remarks. — Mr. E. W. Nelson has most kindly compared our birds with the 

 fine series of true >S'. brewsteri taken by himself and Goldman on the west coast 

 of Mexico and adjacent islands, and agrees with us that the present form is well 

 worthy of recognition. Whether it should be treated as a distinct species or 

 all the forms like Sula leucogastra arranged as subspecies of one bird, is a 

 matter best to be left for a detailed revision of the group. 



Sula etesiaca breeds in large numbers on Gorgonilla ; at the time Mr. Brown 

 visited the place the breeding season was over, though the birds were still 

 abundant about the island. 



FREGATIDAE. 



3. Fregata aquila (Linne). 



No specimens were secured. The breeding season Avas past and the birds 

 coiild not be obtained. It nests in numbers on Gorgonilla. 



