154 GULL GROUP 



stations. Its breeding on the Bass Rock is referred to under the 

 head of the preceding species. Smooth grassy slopes, Hke those 

 on the Bass Rock and the Fame Islands, crowning cliffs, rather than 

 ledges on the cliffs themselves, form the nesting-sites favoured by the 

 lesser black-back ; while herring-gulls and kittiwakes build near by on 

 the scarped rocks. These gulls are ahvaj's social, and may be seen at 

 times inland following in the wake of the plough. Their cries are 

 very similar to those of the herring-gull ; and fish forms the staple food 

 of this species, which will, however, often resort to the neighbourhood 

 of ships for the offal thrown overboard. The nest is an ill -built 



MOUNTED IN THE ROALANO WARD STUDIOS 



LESSKR BL.\CK-B.\CKED GULL. 



structure of dry grass, seaweed, etc., and at the proper season ma}- 

 contain either three or four eggs, the latter being rather an unusual 

 number in this group of birds. It is related that a nest in the Natural 

 History Branch of the British Museum, containing four eggs, was made 

 in a sheep-track, and that, in passing to and fro, the sheep were 

 considerate enough to jump over the back of the sitting bird. As 

 regards the eggs themselves, it will suffice to mention that they 

 measure less than 3 inches in length, but arc otherwise ver\' similar 

 to those of the great black-back, although rather darker coloured. 



Although in length this species does not exceed 22 inches, in 

 colouring it clo.sely resembles the great black -back, from which it 

 differs mainly in the paler back and wings, as well as by the bright 

 yellow of the legs and feet. In winter the head and neck are streaked 



