LARUS GLAUCUS. 215 
Perhaps some of the immature birds remain during the 
summer ; but all the adults disappear by about the 15th of 
April, 
The legs of this species, when adult, are flesh-colour. The 
immature birds of this and the two next species are undistin- 
guishable from each other. 
315. Larus LEUcoPHiEUs, Licht. Southern or Yellow- 
legged Herring-Gull. 
Favier remarks that " this Gull is not very common near 
Tangier, where it consorts with L. fuscus and L. argentatus" 
Being a more eastern species, it does not often come so far 
as the Straits of Gibraltar ; but still it is not rare. 
The adult birds are distinguishable by the colour of the legs, 
which are yellow, as in L. fuscus ; the eyelids are also scarlet, 
as in that species, the back being much lighter in colour, but 
darker than in L. argentatus. 
The size of the three species is about equal. 
316. Larus fuscus, Linn. Lesser Black-backed Gull. 
This Gull is merely included in Favier's list, but it is one of 
the most abundant species of Laridse in the Straits in winter. 
The greater part pass northward by the end of March ; but 
some few pairs remain to nest on the rocks of the African 
shore, laying about the end of April. 
Total length of adult bird about 23 inches. 
Legs and feet yellow ; eyelids red, irides whitish yellow. 
317. Larus marinus, Linn. The Great Black-backed Gull. 
This large Gull is, according to Favier, found about the 
Straits in small numbers from January to March ; and he 
further states that he never saw any but immature birds — 
which agrees with my own observations. 
The immature birds of this species are similar in plumage 
to those of L. argentatus and L. fuscus, but are distinguish- 
able by their large size, being about 27 inches in length. 
318. Larus glaucus, Gmel. The Glaucous Gull. 
This northern (or, rather, Arctic) Gull is not mentioned by 
