LIFE HISTORIES OF NORTH AMERICAN GULLS AND TERNS. 63 



stage that " the primaries more frequently have white or brownish 

 shafts, untinged with the yellow, so prominent in glaucus?"* Kum- 

 lein (1879) says that the first plumage of the young is darker than 

 that of the yearling bird, while the opposite is the case in glaucus. 

 According to Dwight (1906), "the sequence of molts and plumage 

 is precisely the same as in the larger glaucus^ of which it is a small 

 edition. There is, however, no overlapping of dimensions, for even 

 the largest male fails to reach the size of the smallest female glaucus.'^'' 

 The first winter plumage resembles the ju venal, and is acquired by 

 a partial postjuvenal molt. In this plumage the bird looks white, 

 but rather soiled and bufFy or coffee-stained in places. There is 

 considerable variation, and in some individuals the mottling is quite 

 dark. After the first postnuptial molt the bird loses much of its 

 tnottling and becomes nearly white, the candidus and glacialis of 

 early writers corresponding to the hutchinsii of the glaucous gull. 

 Dwight says that " second-year birds more often have adult mantles 

 than do second-year glaucus^ but the creamy or pinkish drab, or 

 white primaries and brown mottled feathers in wings of tail, betray 

 their age." The full adult plumage is assumed in the third winter, 

 and is characterized by a pearl-gray mantle and pure white color 

 of head, breast, tail, and the tips of all of the wing feathers. The 

 bill is yellow. According to Dwight the color of the mantle is some- 

 what darker than that of glaucus. This stage is rarely seen on the 

 New England coast, although full adults of the glaucous gull are 

 not uncommon. 



The recognition of a white-winged gull in the field is not difficult. 

 The general whiteness of the birds as compared with herring gulls, 

 for example, makes them conspicuous. In all cases where tlie diag- 

 nosis is suspected it is necessary to examine carefully the wing tips 

 with the glasses before one can speak with certainty. The entire 

 absence of dark markings on the wing tips at once settles the general 

 diagnosis, but it is often extremely difficult to differentiate between 

 the glaucous gull and the present species. Particularly is this the 

 case if a white-winged gull is seen alone or with others of the same 

 species. Size in absence of other objects for comparison is very 

 deceptive. In company with the glaucous or the herring gull, the 

 Iceland gull is seen to be a little smaller. The glaucous gull is not 

 only larger than the Iceland gull, but is also larger than the herring 

 gull; but here again appearances without careful comparison are apt 

 to be deceptive. In fact, size alone is of little value, for a large male 

 Iceland gull may nearly eqiuil in size a small female glaucous gull. 

 The size of the head, neck, and bill are, however, important field 

 marks, for these are noticeably smaller in proportion to the size of 

 the bird in the Iceland gull than in tlie glaucous gull. 



