LIFE HISTORIES OF NORTH AMERICAN GULLS AND TERNS. 69 



ever, laid by one bird. Only one brood is raised in a season. The 

 eggs are not distinguishable from those of other species of gulls of 

 similar size. The prevailing shape is ovate, with variations toward 

 short ovate on one hand and elliptical ovate on the other. The shell 

 is thin and finely granulated, with only a dull luster. The ground 

 color shows various shades of buff, " olive buff," and pale olive. The 

 eggs are spotted, generally uniformly over the entire surface, with 

 small spots or occasional larger blotches of " wood brown," "' raw 

 umber," " burnt umber," or " seal brown," and with underlying spots 

 of " lilac gray." The measurements of 47 eggs in the United States 

 National Museum average. 72.8 by 50.8 millimeters ; the eggs show- 

 ing the four extremes measure 82 by 51.5, 73.5 by 55, 66 by 47.5 and 

 70.5 by 46.5 millimeters. 



Young. — Mr. George Willett (1912) noted the following incident 

 in the education of the young : 



I was considerably interested in observing the swimming lessons given the 

 nearly grown young by the adult birds. In some cases, where the young seemed 

 afraid to take to the water, they were shoved from the rocks by the old birds. 

 The old bird would then swim beside the young one, occasionally poking it with 

 her bill. I was unable to satisfy myself whether this was meant as a caress or 

 as punishment for poor swimming. 



Plumages.— The period of incubation does not seem to be definitely 

 known. The downy young is " drab gray " above, variegated with 

 " avellaneous," and a paler shade of the same color below, fading to 

 " tilleul buff " on the center of the breast. It is heavily spotted on 

 the back with " fuscous black " and on the head and throat with pure 

 black. The young birds somewhat resemble those of the western 

 gull, but the latter has more of the buffy shades and less of the gray ; 

 and the markings on the back are not quite so heavy. Perhaps in 

 large series they might intergrade. 



Dr. Jonathan Dwight (1906) has fully described the sequence of 

 plumages in this species as follows : 



The juvenal plumage is deep plumbeous gray with broad dark barring or 

 mottling and obscure whitish edgings. The tail is nearly solidly gray, sprinkled 

 basally with white, and the flight feathers, Including the quills, are also dark 

 gray. Birds in this plumage are never so pale (especially the primaries) as 

 the darkest leucopterus, nor are they ever so dark as the, palest of the black- 

 primaried species. They fade to a decidedly brown shade, almost mouse gray, 

 but their color (especially that of the primaries) and the size of their bills, 

 even when young birds, are cardinal points by which to recognize them. The 

 first winter plumage is like the juvenal, but at the prenuptial molt white 

 about the head and body and gray on the back begins to appear in some speci- 

 mens, thus marking the first nuptial plumage. In the second winter plumage 

 unpatterned drab or mouse-gray primaries are most frequent, together with 

 the gray mantle of the adult. The white head and neck, as in the other species, 

 are much clouded with dusky markings, which are lost at the next prenuptial 



