The skuas fly about over the rookery, keeping only a few yards from the ground, and should one of them see a nest vacated and the eggs exposed, if only for a few seconds, it swoops at this, and with scarcely a pause in its flight, picks up an egg in its beak and carries it to an open space on the ground, there to devour the contents. Here then was another need for constant vigilance, and so daring did the skuas become, that often when a penguin sat on a nest carelessly, so as to leave one of the eggs protruding from under it, a lightning dash from a skua would result in the egg being borne triumphantly away. The bitterness of the penguins' hatred of the skuas was well shown in the neighbourhood of our scrap-heap. None of the food thrown out on to this heap was of the least use to the penguins, but we noticed after a time that almost always there were one or more penguins there, keeping guard against the skuas, and doing their utmost to prevent them from getting the food, and never allowing them to light on the heap for more than a few seconds at a time. In fact, a constant feature of this heap was the sentry penguin, darting hither and thither, aiming savage pecks at the skuas, which would then rise a yard or two into the air out of reach, the penguin squalling in its anger at being unable to follow its enemy. At this juncture the penguin would imitate the flying motion with its flappers, seeming instinctively to attempt to mount into the air, as its remote ancestors doubtlessly did, before their wings had adapted themselves solely to swimming. Close to the scrap-heap there was a large knoll crowded with penguins' nests, and it was this knoll that provided the sentries. Very rarely did one of these leave the heap until another came to relieve it as long as there were skuas about, but when the skuas went the penguins left it too. When the skuas returned, however, and without the lapse of a few seconds, a penguin would be seen to detach itself from the knoll and run to guard the heap. That some primitive understanding on this matter existed among the penguins seems to me probable, because whilst there were generally one or two guarding the heap, there was never a crowd, the rest of the knoll seeming quite satisfied as long as one of their number remained on guard. In describing the Cape Adare rookery I mentioned the fact that the pebbles entering into the formation of the beach are basaltic, and therefore of a dead black shade. The result of this is that as the sun's altitude increases, heat is absorbed readily by the black rock, through that clear atmosphere, and the snow upon it rapidly melts. [Illustration: Fig. 36. "HOUR AFTER HOUR, DURING THE WHOLE DAY, THEY FOUGHT AGAIN AND AGAIN" (Page 68)]