Vol. II, Pt. I] GIFFORD— BIRDS OF THE GALAPAGOS ISLANDS 45 



the young birds by a faint gray streak, which gradually whit- 

 ens with successive moults. 



In the manner and extent of its moults and plumages this 

 species seems to accord strictly with Lariis heermanni and 

 the other larger gulls treated of by Dr. Dwight in his paper 

 on The Sequence of Moults and Plumages of the Larid(F 

 {Gidls and Terns). ^ The study of the moults and plumages 

 is of course complicated by the lack of definite data concerning 

 the breeding of the species. It is very evident from the 

 Academy's series that there is great latitude in the time at 

 which different individuals start on a stated moult. Birds 

 taken on the same day and in the same locality sometimes 

 differ widely in their state of plumage. Further indication 

 of an extended breeding season is found in two birds in Juve- 

 nal plumage, one taken on south Albemarle on November 1, 

 the other taken on Chatham on July 7. A pair of adults 

 taken on Charles Island, October 5, were evidently nesting, 

 judging from the bare skin in two places beneath the feathers 

 of the abdominal region. The absence of growing feathers 

 shows that the postnuptial moult had not commenced. The 

 adults of this species do not lose the dark hood at the post- 

 nuptial moult as do the smaller hooded gulls, but on the con- 

 trary replace it with another. 



The following examples of albinism were noted in handling 

 the Academy's series: No. 1759; nearly adult male; white 

 feather in foreneck. No. 1735; adult male; conspicuous 

 white streak in one web of scapular on right side. No. 1770; 

 adult male; white feather in crown. 



Colors of naked parts in life were noted as follows: 1. 

 High-plumaged adult — Bill dark bay shading into black near 

 tip; tip of maxilla burnt sienna; feet dark prune purple, with 

 webs bay beneath and toes rufous beneath; orbital ring dark 

 crimson. 2. Nearly adult female (No. 1793 C. A. S.) with 

 some dark markings in the tail — Bill and feet black; tip of 

 maxilla burnt sienna. 3. Immature — Bill, orbital ring, and 

 feet black ; under sides of webs gray. 



The following condensed measurements in millimeters are 

 taken from forty-nine males and fifty-five females. There 

 seems to be no appreciable difference in the dimensions of 



»Auk, V. 18, pp. 49-63. 



