LESTRIS.] AVES NATATORES. 283 



yellowish white tints, which are probably not assumed till after a certain 

 number of years. This variety is common to both sexes, and individuals 

 may be found shewing every intermediate shade of colouring. (Egg.) 

 Olive-brown, spotted with two shades of darker brown : long. diam. two 

 inches four lines; trans, diam. one inch eight lines. 



Of much more frequent occurrence than the next species, with which 

 it appears to have been confounded by many authors. It is, however, 

 principally confined to the Orkney and Shetland Islands, where it breeds 

 in considerable abundance. Immature birds are occasionally met with 

 on different parts of the English coast. Habits predatory, like those of 

 the Common Skua. Nest constructed of dry grass, on unfrequented 

 heaths. Eggs two in number. Is gregarious during the breeding 



306. L. parasiticus, Temm. (Arctic Skua.) Central 

 tail-feathers projecting six inches or more ; gradually taper- 

 ing from the base; the tips acute: tarsus one inch six 

 lines ; slightly rugose. 



L. parasiticus, Temm. Man. d'Orn. torn. n. p. 796. Faun. Bor. 

 Armr. vol. n. p. 430. Parasitic Gull, Gould, Europ. Birds, 

 part iv. 



DIMENS. Entire length twenty-one inches: length of the bill one 

 inch and six-eighths ; of the tarsus one inch six lines ; of the central 

 tail-feathers twelve inches; of the wing eleven inches nine lines. 

 GOULD*. 



DESCRIPT. Extremely similar to the last species, from which it is 

 principally distinguished by its smaller size, longer central tail-feathers, 

 and shorter tarsi. (Adult male and female.) " Top of the head, and the 

 space between the bill and the eyes, of a deep blackish brown, terminating 

 at the occiput ; the whole of the upper surface of a clear brownish gray ; 

 quills and tail-feathers much darker ; the throat, neck, and under sur- 

 face, of a pure white, with the exception of the cheeks and sides of the 

 neck, which are tinged with a delicate straw-yellow; legs and feet black. 

 The young resemble in colouring the other species of the genus of the 

 same age." GOULD. 



Apparently of rare occurrence in this country ; nor is it known whether 

 it ever breeds with us like the last species. A British-killed specimen is 

 in the British Museum, but I am ignorant from what locality it was 

 obtained. According to Mr. Thompson, it has repeatedly occurred in the 

 Bays of Dublin and Belfast. It is possible that the Arctic Gull noticed 

 by Montagu in the Supplement to his " Ornithological Dictionary," may 

 have been of this species, but in all other cases the bird described under 

 that name by English authors is referable to the L. Richardsonii. Ac- 

 cording to Mr. Gould, the present species inhabits the shores of the 

 Baltic, the rugged coasts of Norway, and the Polar Regions. Habits 

 similar to those of the rest of the genus. 



* The following are the dimensions of a British specimen, in the British Museum, as given in 

 the Faun. Bor. Amer. by Dr. Richardson. " Length, total, twenty inches ; the same, excluding 

 central tail-feathers, fourteen inches ; of central pair eleven inches ; of wing eleven inches six 

 lines ; of bill above one inch ; of bill to rictus one inch seven lines and a half; of tarsus one inch 

 seven lines; of middle toe one inch three lines; of hind toe two lines; of hind nail two lines; 

 transverse diameter of the bill at the front four lines." 



