92 Mr Edmoiidston on the Arctic Gull, ^d. 
fancy it will not be assumed, that this alone is sufficient to esta- 
blish accurate distinctions, in opposition to the other circum- 
stances which I have enumerated, in which they thoroughly 
correspond. But if it shall be found that even this distinction 
xs nugatory — if the two birds shall occur in characters of plum- 
age insensibly passing into each othpr, then, I apprehend, we 
should have sufficient evidence of the accuracy of the opinion 
which I am disposed to maintain, That they are the same spe- 
cies, differing only in age ; the white-breasted Arctic gull being 
the species in its adult dress, the brown individual the same in 
the young and imperfect state. In this opinion I am happy to 
find I am supported by the authority of Montagu, whose in- 
dustry and zeal have so much contributed to elucidate British 
ornithology. 
I have procured specimens of the Arctic gull, in shades of 
plumage intermediate between its young, usually called the 
Black-toed Gull, and the perfect white-breasted adult bird; 
some of the former passing into the characters of the brown 
bird, and these again acquiring the adult appearance. 
They breed in the same situations, and promiscuously ; and 
single pairs, sometimes of two brown, or two white-breasted 
ones, or of a brown and white, with their nest and eggs, are 
often found on one separate hill, so far removed from other 
haunts, more numerously occupied by their species, as to render 
this proof little subject to suspicion. This remark of their pro- 
miscuous pairing will also be strikingly confirmed by traversing 
the heaths where they are most frequent. But this habit, 
though strongly corroborating the opinion I am supporting, is 
not essential to its establishment ; even the opposite fact might 
very naturally be reconciled to its accuracy. A more indirect 
objection may perhaps occur, from the generally correct ana- 
iogy of the other gulls, which are not observed to breed till 
they have attained to permanent and perfect plumage. It will 
be remembered, however, that this bird, and the Skua gull, are 
so strikingly distinct in their general aspect, and in many of 
their habits from the gull tribe, that they have been very pro- 
perly formed, by later naturalists, into a separate genus (Lestris); 
and hence this apparent objection does not apply. 
If they are separate species, we should naturally expect to 
