This is the commonest of the Skuas, occurring on all the Scottish coasts and being fairly common in the east of England every autumn. In Ireland and the west of England it is only an irregular straggler.
It breeds in the Shetlands, Orkneys, and the north of Scotland, some moor at no great distance from the sea being chosen as a summer home. No nest is made, but a depression is formed in the moss or grass on which the two brownish green eggs, blotched with darker brown, are laid. The young when first hatched are covered with dark brown down.
In its habits and food it does not differ from the other Skuas.
This species is dimorphic, one form having light under parts, and the other being of a uniform sooty brown all over. The light-coloured birds predominate in the north of their breeding area and the dark ones in the south, but when they meet they breed indiscriminately, and intermediates of all shades are found. The central tail feathers are longer than the rest. Length 20 in.; wing 13 in.
The young vary considerably, but are usually brown, mottled and spotted with chestnut, while in some the chestnut colour is almost entirely wanting.
THE LONG-TAILED OR BUFFOUS SKUA
Stercorarius parasiticus (Linnæus)
This is a rare species to all our shores, but a few, chiefly immature birds, visit the east coast yearly, and in some seasons become quite common. It is a circumpolar species, breeding on the tundras throughout Europe, Asia, and America, and migrating in winter as far south as the basin of the Mediterranean.
In its habits it resembles other Skuas, but in addition to robbing Gulls, it feeds largely on beetles and worms, and the young eat a large quantity of crowberries when in their summer-quarters.
The adult has the top of the head black, cheeks and hind neck buffish yellow, mantle and tail, the two central feathers of which are much elongated, grey brown, wings darker. Under parts chiefly white, brownish on the flanks and belly. Length 23 in.; tail 8·5 in.; wing 11·9 in.
Immature birds are barred above and below with brown and yellowish white. It is sometimes rather difficult to distinguish between the young of this and the preceding species; the present species is, however, always much greyer and less rufous, and has the shafts of the two outer primaries white, the rest being dusky, whereas in the Arctic Skua the shafts of all the primaries are white.