LIFE HISTORIES OF NORTH AMERICAN PETRELS AND PELICANS. 213 



to develop and enable the younij bird to fl}' at an early a^e. This 

 Juvenal ijlumage is too variable in shade to definitely name the colors, 

 but in a general way it is sooty brown above, including the wings 

 and tail, and lighter or drab below ; there is no white in this plumage 

 at first. The changes that take place subsequently are not well under- 

 stood, nor is it definitely known how long it takes to complete the 

 changes. Until more material is collected for study we can make 

 onl}^ a provisional guess at what takes place. Apparently some prog- 

 ress is made during the first year, either by a prenujDtial molt or by 

 a more or less continuous molt during the year, for young birds seem 

 to acquire considerable white before the}^ are a yenv old. Probably 

 no white is acquired before the first prenuptial molt, Avhich seems to 

 be quite extensive. Doctor Fisher (1906) describes a young bird, 

 which was probably about a year old, as follows: 



Whereas the adult is piu'e white, except the dark grayish-brown quills and 

 greater wing coverts, this inunature bird, in much-worn plumage, has the head 

 and neck hair brown, the feathers edged with whitish ; throat the same ; .iugulum 

 white; a sepia band across breast; abdomen white ; back deep bister, the feathers 

 edged with wood-brown ; wing coverts and tertials sepia, edged with light brown ; 

 rectrices same, tipped with white ; remiges brownish black. The immature in- 

 dividuals must belong to a late brood of the previous year. 



At the next molt, the first postnuptial, another brown plumage 

 somewhat darger than the first is acquired on the upper parts, with 

 probably an increasing amount of white on the under parts, head, 

 and neck; probably the white tail, rump, and under tail coverts are 

 assumed at this molt, but jierhaps not imtil the next molt, the second 

 prenuptial. 



In this second nuptial plumage, in which the tail, low^er back, 

 rump, vent, and both tail-coverts are white, birds have been fre- 

 quently found breeding. Mr. M, J. Nicoll (1906) noted that on 

 Glorioso Island " at least 90 per cent of the gannets are brown- 

 plumaged birds with white tails." Although these white-tailed 

 broAvn birds are generally conceded to be fSula piscafor and are so 

 labeled in collections, I have always had a lurking suspicion that 

 they might represent a distinct species and that perhaps Mr. C. J. 

 Maynard (1889) was justified in naming them SiiJa coryi. 



Probably during the following year, the third year of the bird's 

 life, the adult plumage is fully acquired; I have seen one bird, ap- 

 parently about three years old, collected on July 25, which is in 

 worn adult plumage except for some dusky mottling on the back. 

 This bird, which had not yet molted, would probably have assumed 

 the fully adult plumage at the next molt, the third postnuptial. 

 I have seen immature birds undergoing the postnuptial molt as early 

 as July 25, as late as October 9, and at various intermediate dates. 

 Adults I have seen molting in June and in August. Undoubtedh' 

 83969—22 15 



