256 THE ZOOLOGIST. 
This cannot, of course, be taken as being a standard of the 
measurement of this species, as individuals of the same age 
differ greatly. However, it seems to be a broad outline of 
the changes of size. Among the number of examples my 
brother has examined, the young bird in the last year of its 
immature plumage most frequently was larger than an adult 
of the same sex. In the immature birds the colour of the 
iris, of course, is brown, and all the adults we have examined 
have had very light yellowish irises, not red, as is stated by 
Saunders in his ‘ Manual’ as the usual colour of the eye of this 
species. H. V. Charlton once observed a Greater Black-backed 
swooping at a Guillemot which was on the water close by the 
shore. The assailant would rise up and come skimming near 
the surface at a great speed towards the Guillemot, which, on its 
almost striking it, would suddenly dive. This continued for 
some time, and a gentleman standing by asked if it was a Sea- 
Eagle! Eventually it departed, and the Guillemot was left 
in peace. 
Guaucous Gui (L. glaucus).—A rare winter visitant ; imma- 
ture birds occasionally pass along the coast. I have record of two 
mature birds, which Mr. J. Duncan informs me he examined, and 
which had been shot at St. Mary’s Island in 1872; and on Jan. 
22nd, 1911, H. V. Charlton observed an immature bird feeding 
with immature Greater Black-backs at the sewer-mouth at 
Whitley Bay. A wave broke over it once, and completely im- 
mersed it, but it rose immediately and shook itself. Its body and 
wings appeared longer than the other Gulls, and it was creamy 
in colour. It kept more or less to itself, and flew round the 
others several times. The first occurrence was in the year of 
the great influx of this species on the east coast of Scotland. 
IckLaND Gui (L. leucopterus).—A rare winter visitant ; two 
immature birds presented to Newcastle Museum by Selby were 
shot at Cullercoats in January, 1880. My brother, H. V.Charlton, 
shot a very fine immature specimen, in the third year, in the 
fields behind Cullercoats on Feb. 10th, 1906. | 
Kirtrwake Guu (Rissa tridactyla).—A not uncommon resi- 
dent, but keeping well out to sea. It breeds at the Farne 
Islands, to which the adults depart for the summer months. 
This part of the coast is indebted to the close proximity of the 
