The Zoologist — September, 1866, 371 



What I can learn of this bird is that it has no known habitat, but is 

 rare wherever it occurs ; that it has never authentically been found 

 breeding; that eggs said to be of the masked gull are only smaller 

 than those of the blackheadcd gull, a very feeble ground of distinc- 

 tion, as the egg of the blackheaded gull is often smaller than that of 

 the so-called " masked " gull : that the great distinction lies in the 

 size, L. capistratus being smaller than L. ridibundus ; in the colour of 

 the feet and bill, which in the former are dull red, in the latter arterial 

 blood-red in summer; in the brown of the head assuming a masked 

 appearance in L. capistratus, a hooded in L. ridibundus : the real 

 brown of L. capistratus often takes the place of the sooty brown of L. 

 ridibundus, so is consequently not a distinction. In respect of size, 

 I can only say that I have shot many blackheaded gulls in the winter 

 dress identical with the masked gull in this respect, and as there is no 

 known difference in winter but this I might call these masked gulls; 

 but then, unfortunately, the same thing occurs in summer when the 

 hood is to the full ; so that size is no distinction. With regard to the 

 colour of the feet, I can also say that the blackheaded gull in spring 

 (particularly at two years old) has the feet and bill the colour of L. 

 capistratus, caused by the transmuting of the dull scarlet of winter to 

 the arterial blood-red of summer; in autumn vice versa. With regard 

 to the mask I have shot blackheaded gulls in autumn (the lime, too, 

 when masked gulls are generally shot) with the masked appearance of 

 L. capistratus : this I always found was caused by the autumn moult, 

 the back of the head turning white before the front. In spring birds 

 transmuting often assume the mask before the hood. In fact, I have 

 seen gulls iu spring and autumn with the back of the head black and 

 the front white, one side of the head brown the other white, the fore- 

 head and round the eyes brown, making a perfectly spectacled gull ; 

 and, lastly, the hood consisting of brown and white feathers. Last 

 autumn I could have recorded two perfectly masked gulls, but on 

 blowing up the feathers I saw the white ones sprouting, and at the 

 nape, in one, was one hrown feather still. On this subject I have 

 worked hard and killed many poor blackheaded gulls, and also used 

 the telescope freely, and have come to the conclusion, with Thompson, 

 that our so-called " masked" are only blackheaded gulls, and I fear 

 many of those in collections would not bear a critical examination. I 

 have seen some admirable "get ups" with dealers; blackheaded gulls 

 that were in strong moult about the nape, with the few remaining 

 brown feathers pulled out, thus leaving the mask. Many acids also 



