Mr Edmondstoii ot), the Colymhue Grylle^ ^c. lOS 
account for this singular and radical deviation from the habits 
of other similar birds. 
The individuals I have met with in Zetland during vdnter, 
especially in the beginning of that season, are less sensible to 
danger, and dive less readily on the fire. These facts, I remem- 
ber, struck pie before 1 had formed any idea regardh^g the ' 
migration or change of plumage of this* species, and are charac- 
teristic ©f yr)ung birds. 
Frequently black guillemots are found during every period 
iof the winter ; and that spch appearances are rather exceptions 
to a general law of migration, apparently not very imperative, 
than to that ©f change of plumage, seems too obvious to be in- 
sisted on. 
The general habit of this genus is to carry the young to sea 
«ome time before they are capable of using their wings for flying, 
at least to any considerable distance; and, hence from deriving 
their food chiefly from diving, and from the comparative ab- 
sence or disuse of flying, we naturally might expect that the 
greater part of the young would be unfit for distant or pro- 
tracted migration, at the period of the disappearance of the old 
birds. 
The only objection that occurs to foe opinion I have adopted 
seems easily removed. It is, that the young should so far differ 
from the adult birds in their habits of migration. But, what- 
ever opinion be held as to its cause, the fact is certain, that the 
numbers found in Zetland in autumn are much less than those 
met wifo in that country during winter. And to account for 
this, foe supposition, as the general principle, of some of the 
'©Id and young promiscuously departing and remaining, is sure- 
ly quite as inadequate as the other, and beside?, requires the ad- 
mission of what is chiefly disputed, that foe plumage of the old 
is changed to that of the young, But there is nothing, a 'priori^ 
to prevent foe suppoation, that the ypung of certain species of 
birds should inhabit, at certain seasons, countries diffei’ent from 
those resorted to by the parent birds ; and this presumption is 
amply confirmed by experience and analogy, and derives still 
more forcible confirmation as we descend in the zoological scale. 
Why, indeed, young birds should not differ in habits of mi- 
gration, as they do so frequently in characters of plumage from 
