5 i8 GULL TRIBE. 



it from fright to disgorge the recently-swallowed fish they descend to catch 

 it, being frequently so rapid and certain in their movements and aim as to 

 seize their prize before it reaches the water." Of the two members of the group 

 breeding within the limits of the British Islands, the largest is the great skua 

 (8. catarrhactes), its only resort within those limits being the Shetlands. 



Measuring upwards of 24 inches in length, the great skua has the two 

 central tail-feathers less than an inch longer than the others, and may be further 

 distinguished by the white bases to the flight-feathers ; the general colour being 

 dark brown. It nests in a hole of about a foot in diameter, laying one or two eggs 

 on a lining of moss and heather. It is to this species that the two southern 



POMATORHINE SKUA. 



forms alluded to above are allied. Taking the other species in their order of size, 

 the long-tailed skua (S. parasiticus), which measures 22 inches in length, has the 

 two central tail-feathers upwards of 9 inches longer than the rest. Essentially an 

 Arctic species, this bird is but a very occasional visitor to the British Islands. 

 The pomatorhine skua (8. pomatorhinus), on the other hand, is a regular winter 

 visitor to the last-named area ; it may be distinguished by the two central tail- 

 feathers being twisted upwards and exceeding the others in length by 4 inches, 

 the total length of the bird being 21 inches. Lastly, we have Richardson's skua 

 (8. crepidatus), measuring an inch less than the last, and distinguished by the two 

 central tail-feathers being only 3 inches longer than the others. Circumpolar and 

 subarctic in its breeding-range, this species is much more abundant in Britain 

 than either of the others, nesting not only in the Hebrides, Orkneys and Shetlands, 

 but likewise on the mainland in the counties of Caithness and Sutherland. 



