186 CHAPTERS ON THE NATURAL HISTORY 



There must have been a great many forms that became extinct 

 between the times of the cretaceous and the tertiary, and many 

 of these yet remain to be found. 



The gull selected for illustration in the present connection is 

 the species known as Boss's gull, or Ross's rosy gull, it having 

 been likewise called the Wedge-tailed gull, from the fact that 

 its tail is of the cuneate form. Beyond this latter peculiarity, 

 and its lovely rose-tinted breast in the adult, it has most of the 

 characters common to any of our smaller and typical gulls. Dur- 

 ing the breeding season it has a plumage somewhat different 

 from that, as shown in the figure; the adult being white, beauti- 

 fully shaded with rose, with a pearly-blue mantle, and a black 

 collar about the neck. The bill is black, while the feet, eyelids, 

 and gape are a bright red. It has a length of about fourteen 

 inches. This is a circumpolar species, of the Arctic regions, a 

 tVw stragglers only occasionally coming south to the most north- 

 ern parts of the North Temperate Zone. At one time it was ex- 

 ceedingly rare in museums and collections, but about ten or more 

 years ago a large number were taken at Point Barrow by one of 

 the United States Government expeditions. I believe that its 

 breeding stations still remain unknown, and we yet remain in 

 ignorance of many of the habits of this, one of the most beautiful 

 of all the existing gulls. 



Red, white, black, pearly-blue, and rarely, rose, are the pre- 

 vailing colors of this family of birds. The young may show vari- 

 ous shades of brown or gray, or are dusky. Adults in the breed- 

 ing season are, as a rule, white, with a mantle of pearly-blue. 

 Some of the species have black heads, and often much black is 

 seen at the wing-tips or the primary feathers of the same. Marked 

 changes of plumage take place with age, and different seasons, 

 though usually the sexes are always alike. Several years elapse 

 before the mature plumage is attained, the color of the bill and 

 feet changing at the same time. The latter are invariably 

 webbed, and not illy fitted for ambulatorial purposes. Commonly 

 the tail of a gull is even, rarely forked or wedge-shaped, and 

 iH'ver has median projecting feathers as in many of the jaegers. 

 All the bigger forms have powerfully hooked beaks, apt to soize 

 the small fishes upon which they largely feed. Indeed, the Great 

 bin rk -backed gull is a very marine raptorial pirate, who will not 

 only rob other gulls and their kind of their prey, but will make 

 excursions inland and hunt for the young and eggs of other birds 



