observed during the Voyage of the 'Valhalla.' 691 



the white plumage, I do not think that there are sufficient 

 grounds for separating them. 



Is the Glorioso bird passing by evolution from a white 

 to a constant dark form ? If so, why ? It cannot be a case 

 of isolation, as Glorioso is not much more than fifty miles 

 from Assumption, where the Gannets are all white or 

 speckled birds, moulting to white, and Sula piscator is one 

 of the most active and quick-flying Gannets that exists. 

 The climate is the same at Glorioso as at Assumption, and 

 the food is probably the same. 



I give below a short description of the plumages of my 

 specimens : — 



? imm., Glorioso, March 10th. — Slightly darker than that 

 of young examples from the Atlantic (S. Trinidad) and slightly 

 greyer; new feathers on back slaty-grey; old feathers on neck 

 much worn and tipped with golden straw-colour, new feathers 

 slaty-grey with no gold tips ; tail dark brown. 



This is evidently a bird going through its first moult. 



$ breeding, Glorioso, March 10th. — Darker grey than the 

 young bird ; new feathers appearing dark slaty-grey, old 

 feathers on neck tipped with golden colour ; no gold colour 

 on new grey feathers of neck. Tail, lower back, rump, vent, 

 and under and upper tail-coverts white. 



— Fregata aquila (Linn.). 



Fregata aquila minor Kidgway, Proc. U.S. Nat. Mus. 

 xviii. p. 525 (Glorioso). 



Fregata aquila Grant, Cat. B. B. M. xvi. p. 443. 



Bill, iris, tarsi, and toes black ; pouch brilliant brick-red. 



The Large Frigate-bird is subject to much variation in 

 size in different parts of the tropical Atlantic, Pacific, and 

 Indian Oceans, especially as regards the dimensions of the 

 bill. I can, however, see no other difference, and therefore 

 prefer to use the name F. aquila for the examples from 

 Glorioso. 



At the time of our visit these birds were breeding in 

 numbers in the tallest trees on the island. Many were 

 sitting on their nests and on the tree-tops Avith their scarlet 



