This species inhabits the North Atlantic ocean chiefly on the European side, being abundant in the Mediterranean and in the British Isles. These birds deposit their single pure white eggs in crevices among the cliffs, on the graound or in burrows dug by themselves. Size of egg 2.35 x 1.60. Data. - Isle of Hay, North Scotland. June 1, 1893. Single egg laid at the end of a three foot burrow.