188 ORNITHOLOGICAL EXPLORATIONS. 



(Inring: the summer. This is not to be uiulerstood as a positive state- 

 ment that tlie same parents rear two sets of young every year — although 

 I believe that most of them do — but simply that I have found the colo- 

 nies of this species having eggs and downy young at two different times. 

 Tlie first season commences early in May, the young of this brood 

 being fully fledged in the latter part of July. In the middle of this 

 month, however, the colonies again contained all stnges, from fresh eggs 

 to newly-lnitched young. During the first days of August I found 

 downy young of almost the same age and still without feathers, while 

 on the 1:1st of August, 1882, 1 visited a numerous colony at PoludjonniJ, 

 Bering Island, in which the oldest young were about half fledged. 

 These would not be able to fly before the first week of September. Be- 

 tween the two periods, young in all stages of development will be found 

 in the colonies, but i)roportionately few in number. It will thus be seen 

 that it is safe to assume that the difference in age between the earliest 

 and the latest born young in one year amounts to three months, at least. 



We are now iirepared to understand that we can find two birds un- 

 dergoing the corresponding moult at times as much apart as the birth- 

 days of the same two birds. If the first moult occurs, say, ten 

 months after the bird broke the shell, the bird born in the middle of 

 May will moult in the middle of March next year, while the one born 

 in the middle of August will not moult before the middle of June next 

 year. And this conclusion is borne out fully by the observed facts. As 

 will be seen from th(^. details relating to the bir<ls collected by me, as 

 given below, I shot birds in the latter part of February, both younger 

 and older, which were just in the first stage of moulting,* wliile, on the 

 other hand, I have a skin before me in full moult from young to adult 

 l^lumage, as late as July, a discrepancy hardly to be accounted for, ex- 

 cept by the above explanation. 



When about ten months old, the first plumage, which is of the dark 

 grayish sooty color, with some green and purplish .reflections in the 

 fresh plumage, changes into the resplendent garb of the adult,t from 

 which it then is nndistinguishable, except by not having the bright 



*In fact, I should not have been able to ascertain the fact had it not been that I 

 always was on the lookout for the moult when skiuninjf the fresh bird, and making 

 my notes right on the spot. 



tMr. N. S. Goss in a paper in "The Auk" (1884, p. 1(54) thinks that the birds (Ph. 

 pclaaicus resjjfevflens) must be two years at least in acquiring the adult pluuiage, be- 

 cause many of the young birds were still of a brown color on the (5th of June. The 

 explanation is simply that the greater part had not yet commenced their moult as 

 early as that date. 



