The Arctic or Richardson’s Skua — Stercorarius Crepidatus (J. F. Gmelin)
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.