RISSA TRIDACTYLA. 301 



345. Larus fuscus, Linnseus. The 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. 



Head and neck white ; mantle slaty black ; legs and feet yellow ; 

 primaries nearly uniform dark brown. 



Young. Like last. Length 21-23 inches. 



346. Larus marinus, Linnseus. 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 ; this agrees with my 

 own observations, except that I have occasionally seen adults. 



Resembles the last, but larger. Legs and feet flesh-colour ; distinct 

 wedge on third and fourth primaries. 



Young. Like last. Length 26-33 inches. 



347. Larus glaucus, 0. Fabricius. The Glaucous Gull. 



This Arctic Gull is not mentioned by Favier, but was once 

 obtained by him in immature plumage near Tangier. 



Adult. Entirely wJiite, except grey mantle ; head and neck streaked 

 w T ith ash-grey in winter. 



Young. Dull white, mottled with pale brown ; primaries greyish white ; 

 for a short time before assuming adult plumage the mantle is entirely 

 white. Length 26-33 inches. 



348. Rissa tridactyla (Linnseu*). The Kittiwake. 



" This species is nearly as common during winter in the Straits 

 as the Herring-Gull, appearing during the month of November 

 and leaving in March." Favier. 



The Kittiwake is to be seen in the Bay of Gibraltar during 

 winter, sometimes in great abundance, at other times hardly any 

 are to be found ; their presence or absence is due to the state of 



