Out of the breeding-season it shows itself in most parts of the North Atlantic, but never seems to stray farther south than Gibraltar or Morocco, and it is therefore a matter of much interest to find the Southern Ocean inhabited by a bird - the "Port Egmont Hen" of Cook's Voyages - which so closely resembles the Skua as to have been for a long while regarded as specifically identical with it, but is now usually recognized as distinct under the name of S.
Richardsoni, a name that correctly applies only to whole-coloured examples, for this species too is dimorphic. Even its proper English name 4 is disputable, but it has been frequently called the Arctic gull or Arctic skua, and it is by far the commonest of the genus in Britain, and perhaps throughout the northern hemisphere.
They are the home of myriads of sea-birds and one of the nesting-places of the bonxie, or great skua (Lestris cataractes), which used to be fostered by the islanders to keep down the eagles, and the eggs of which are still strictly preserved.
Skua, is not known to exhibit the remarkable dimorphism to which the two preceding are subject.