104 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



With one exception all the specimens of Fregata aquila in 

 the Academy's collection are from the Galapagos Islands. 

 Birds in juvenal plumage, and assuming juvenal plumage, 

 have the entire head and neck a rich cinnamon-rufous. No 

 exception to this is found in the Academy's series. 



Five adult males and six adult females from the Galapagos 

 Islands measure in millimeters as follows: Males — Wing 

 595-660 (633) ; tail 400-490 (463) ; culmen 90-114 (104) ; 

 tarsus 18.6-23 (21.2) ; middle toe 46-51.4 (49.1). Females- 

 Wing 680-710 (696); tail 480-515 (503); culmen 122- 

 127 (125) ; tarsus 21-23.7 (22.7) ; middle toe 51-57 (54.8). 



A series of sixty-seven eggs from San Benedicto and a series 

 of thirty-seven from the Galapagos Islands give practically the 

 same average length and breadth. Among the sixty-seven 

 San Benedicto eggs, however, the difference between the ex- 

 tremes is greater, as can be seen from the following measure- 

 ments in millimeters: San Benedicto — Length 63.1-77 (69.6) ; 

 breadth 43-50.6 (47.2). Galapagos— Length 64.1-74.6 

 (69.3); breadth 45.5-49.4 (47.5). A set of two eggs from 

 San Benedicto measured 68.9X47.2, 71.1X46.2. 



Phaethon aethereus: Red-billed Tropic-bird 



Abingdon, Albemarle, Barrington, Brattle, Champion, 

 Charles, Chatham, Culpepper, Daphne, Hood, Indefatigable, 

 Onslow, Tower, and Wenman islands. 



Red-billed Tropic-birds were not seen in any numbers ex- 

 cept at Daphne, Hood, and Tower islands. They, were seen, 

 however, through the entire year. Usually they travelled 

 singly or in couples, but not in flocks. When met with away 

 from land, they frequently flew about the vessel two or three 

 times, keeping quite high in the air. The farthest point south 

 of the Galapagos Islands at which we saw these birds was in 

 2° 36' south latitude. 



During the breeding-season at Daphne Island I saw birds 

 circling about holes on the hillsides without beating their 

 wings. Whenever they came opposite certain holes they 

 would flutter their wings to check their flight, and come to a 

 standstill for an instant, as though about to alight, but they 

 would continue their circle. This was repeated ten or twelve 



