284 Mr. Montagu's Observations 
but in some so near it as not to admit of a specific mark of di- 
stinction : the bill and legs dusky. 
In cases of this nature we can only form opinions upon long 
and continued observations, noted with care and circumspection : 
upon such observations, therefore, we found our opinion, though 
it would be difficult to produce more than strong presumptive 
proof on such a question ; but by pointing out our suspicions, we 
may stimulate others to join in the pursuit of investigating such 
abstruse subjects. 
Black-headed Gull. 
Larus ridibundus. Gmel. Syst. p. 601. Ind. Orn. \i.p. 811. 
Black-headed Gull. Br. Zool. ii. No. 252. Lath. Syn. vi. p.3S0. 
Gull, black-headed. Orn. Dictionary. 
From the very great confusion which seems to have arisen in 
some species of the Gull tribe, occasioned by a very considerable 
variation in plumage at different ages and seasons, we trust it will 
not be unacceptable to this Society and to the critical ornitholo- 
gist, if from long and strict attention to several of this genus, 
which for many years have almost daily been presented to our 
view, we should endeavour to clear away a little more of that 
mist which has, for so long a period, veiled in obscurity those 
birds which are usually known by the names of Black-headed 
Gull, Larus ridibundus, Red-legged Gull, Larus cinerarius, Brown- 
headed Gull, Larus erythropus, Brown Tern, Sterna obscura, all of 
the Gmelinian system ; and the Brown Gull of the Second Sup- 
plement to Latham's General Synopsis. 
It is a claim which science has upon the naturalist — the endea- 
vour to elucidate any of the more obscure objects of the crea- 
tion: in our attempt, therefore, to throw light upon a subject 
which has caused so many various opinions, we beg leave to say, 
that 
