32 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



The measurements of 32 eggs in various collections average 60.5 

 by 43.6 millimeters; the eggs showing the four extremes measure 

 69.3 by 41.5, 62.6 by 44.6, 57 by 43. and 60.5 by 40 millimeters. 



Plumages. — Prof. CoUett (1888) describes the downy young 

 as " white all over ; the down white to the root " ; and says that 

 " even in this first stage the young in down may be distinguished 

 from the young of other species by the strong and hooked claws, 

 especially on the hind toe, the somewhat marginated web on the 

 toes, and the forward nostrils. The downy covering is particularly 

 close; L. eburneus in this respect is more closely related to the other 

 species of Larus than to Rissa, the hairlike tips being shorter." 

 A downy young bird in Doctor Bishop's collection, collected on King 

 Charles Island on August 3, 1901, is covered with long, soft down, 

 evenly colored above and below, " pallid mouse gray " shading into 

 " pearl gray " at the base of the down. This is an older bird, how- 

 ever, as the first feathers are appearing on the scapulars. 



Mr. Howard Saunders, in his edition of Yarrell (1871) says: 



The nearly fledged young are described by Richardson ^ as having ash-gray 

 backs ; but with regard to the subsequent stages of plumage there is an 

 absence of satisfactory details, and the editor can only place the following 

 facts before his readers : In the autumn of ISSO Mr. Leigh Smith brought back 

 from Franz-.Josef Land a bird which was supposed to be the survivor of 

 several young taken from the nest, and which was presented to the zoological 

 gardens. Its prevailing tone was gray, owing, perhaps, to the saturation of 

 the plumage with grease and dirt acquired on board the steam yacht, where 

 the bird is said to have frequented the stokehole ; but after constant washing 

 since its arrival at the gardens the bird still remained of a smoke gray, 

 nearly as dark as a fulmar petrel on the upper parts, and especially so on the 

 tail coverts, the feathers of the back and wing coverts having slightly darker 

 shafts, and the head bearing not merely a mask but a short hood of a darker 

 gray than the neck and the underparts. The tail was reduced by abrasion 

 to a mere stump. Such was the description given by the editor when the bira 

 was supposed to be from three to four months old,'' and its correctness can be 

 corroborated by other observers. It was naturally expected that at the next 

 moult the bird would pass into the well-known spotted plumage, but no spots 

 made their appearance, and this example at once assumed the pure white 

 plumage which it now (April, 1884) displays. This omission of the spotted 

 stage may, perhaps, be owing to captivity in a comparatively warm climate; 

 the editor is unable to account for it. 



The ordinary immature or first-winter plumage is white, heavily 

 mottled with dusky or dark grayish spots on the sides of the head 

 and throat, concentrating into almost solid color in the loral region ; 

 scattering spots of the same slate-gray are on the hind neck and 

 upper back. The scapulars have subterminal dusky spots, as do 

 also many of the lesser and nearly all of the greater wing coverts and 

 tertials. The primaries, secondaries, and rectrices are broadly 



1 Journal of a boat-voyage, p. 281. ^ Zoologist, 1880, p. 484. 



