150 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



eggs are smaller and more elongated, both ends of the egg being almost identi- 

 cal in shape. This set is differently marked also. The spots are dingy and 

 not clearly defined as in the remainder of the series. In all, they are the hand- 

 somest eggs of any species of this genus which I have ever seen. 



The measurements of 52 eggs, in various collections, average 59.2 by 

 42.7 millimeters ; the eggs showing the four extremes measure 64 by 

 45 and 53 by 37.5 millimeters. 



Plumages. — The downy young is covered with short, thick down, 

 which on the head, throat, breast and flanks is "pinkish buff" or 

 " pale pinkish buff," becoming paler toward the belly, which is pure 

 white. The back is grayish white, mottled with dusky, and there are 

 a few dusky spots on the top of the head. I have seen no specimens 

 illustrating the change into the first plumage, 



Coues (1903) says of the young of the year: 



Entire plumage deep sooty or fuliginous-blackish; all the feathers, but 

 especially those of back and upper wing coverts, edged with grayish-white. 

 Primaries and secondaries black, as in adults, with only traces of white tips 

 on the former. Tail black, very narrowly tipped with dull white. 



Birds that I have seen in what I call the juvenal plumage have the 

 greater and lesser wing-coverts and the feather edgings "olive 

 brown." They apparently change, by a partial and gradual molt, 

 from this into the first winter plumage between June and October, 

 the wing-coverts becoming grayer, the light edgings of the feathers 

 disappearing by wear, and more or less white appearing on the 

 throat and chin. During the first spring the wholly black bill of 

 the young bird becomes dull reddish on the basal half. This plumage 

 is worn until the next simamer, the first postnuptial molt, if it may 

 be so called, beginning in June. This complete molt produces the 

 second w^inter plumage, which is similar to the first winter, except that 

 the primaries and rectrices are blacker and very narrowly edged 

 with pale brown ; the upper tail-coverts are more slaty ; the head and 

 nape are clear slate-black, the mantle is darker slate-black and the 

 bill is practically like the adult. 



A year later the young bird assumes a third winter plumage, simi- 

 lar to that of the winter adult, except that the dark mottling on the 

 head is more extensive, including the whole head and throat, and all 

 the colors are darker. The white predominates on the throat, but 

 the rest of the head is very dark. The wings and tail of the adult 

 plumage are assumed, but there is great individual variation in the 

 extent of the white tips of the primaries and the rectrices, though 

 the latter are always broadly tipped with white. At the next pre- 

 nuptial molt, which is only partial, including mainly the head and 

 neck, young birds become indistinguishable from adults; they are 

 then nearly 3 years old. 



I 



