But there was one enemy besides man whom the loons had cause to fear, even on their secluded islet. They hated the mink with a well-founded hate. He could easily swim out to discover and rob their nest; and if he should find it for a moment unguarded, his agility would enable him to keep well clear of their avenging wrath. On the nest neither male nor female feared to meet the mink’s attack, their lithe necks and unerring quickness of thrust being sufficient defence even against so formidable a robber. But their movements on land—an awkward, flopping series of waddles—were so slow that, in the case of a mink arriving, the precious eggs would be safe only while actually covered. A big mink had been seen that very morning, prowling down the opposite shore, and both birds were uneasy. They seemed now to be taking counsel upon that or some other equally important matter.

For the next few days, however, the life of the loons was tranquil, with good fishing to content their appetites and no untoward event to make them anxious. Then came a day when the patient mother on her nest could not conceal her happiness and her excitement, when the male, forgetful of meals, stood for hours at a time in interested expectancy beside the nest. The strong chicks within the eggs were beginning to stir and chip the shell. It was not the day that the big mink should have chosen for his expedition to the islet.

For several weeks the mink had been on the point of swimming out to explore that little patch of rocks and grass and bushes, sentinelled by one dark fir-tree. Such a secluded spot, out of reach of most forest prowlers, might well afford something special in the way of good hunting. Hitherto one thing or another had always diverted him from his purpose, and he had gone off on another trail. But to-day nothing intervened. His long, lithe, black body curving like a snake’s, he ran down the bank, lifted his triangular vicious-looking head for a survey of the lake, and plunged into the water with a low splash.

Now, the vision of the mink, though sharp enough at close quarters, has nothing like the power and penetration of the loon’s. The mink could see the islet, the rocks, the bushes, the sentinel fir-tree, but he could not make out the figure of the loon standing beside the nest. The loon, on the other hand, could see him with absolute distinctness, as if not more than fifty feet away.

As has been already noted, the day was not well chosen for the mink’s trip to the islet. The loon stiffened himself with anger, and his round bright eyes hardened implacably. The mother settled down closer over the stirring eggs, and turned her head to stare malevolently at the long pointed trail which the swimmer’s head was drawing on the lake surface. Her mate stood for some seconds as motionless as a charred stump. Then, slipping noiselessly down the bank, he glided into the water and dived from sight.

The lake was deep at this point, the main channel of the stream—upon which the lake was threaded like a great oval bead on a slender string—running between the islet and the mainland. The loon plunged nearly to the bottom, that he might run no risk of being detected by the enemy. More than ever like a torpedo, as he pierced the brown depths, he darted forward to the attack. Two or three great lake trout, seeing the approach of the black rushing shape, made way in terror and hid in the deepest weed-patch they could find. But the loon was not thinking of fish. The most tempting tit-bit in the lake at that moment might have brushed against his feathers with impunity.

At last, still far ahead of him, he saw the enemy’s approach. As he looked upward through the water, the under surface was like a radiant but half transparent mirror, on which the tiniest floating object, even a fly or a wild-cherry petal, stood out with amazing distinctness. The dark body of the swimming mink was large and black and menacing against its setting of silver, and the ripples spread away from his chin, ever widening, till they faded on the shore behind him. The loon kept straight on till the mink was almost above him, then he turned and shot upward.

Thinking, doubtless, of some wild duck’s nest, well filled with large green eggs, which he would devour at his ease after sucking the blood of the brooding mother, the mink swam on steadily toward the islet. The worn gray rocks and fringing grass grew nearer, and the details began to separate themselves to his fierce little eyes. Presently he made out the black shape of the female loon sitting on her nest and eying him. That promised something interesting. The blood leaped in his veins, and he raced forward at redoubled speed, for the mink goes into his frays with a rampant blood-lust that makes him always formidable, even to creatures of twice his weight.

It was just at this moment that his alert senses took note of a strange vague heaving in the water beneath him, a sort of dull and broad vibration. Swiftly he ducked his head, to see if the whole lake-bottom was rising up at him. But he had no time to see anything. It was as if a red-hot iron was jabbed straight upward through the tender back part of his throat, and a swarm of stars exploded in his brain. Then he knew nothing more. The loon’s steel-like bill had pierced to and penetrated the base of the skull, and with one convulsive kick, the robber’s body straightened itself out upon the water. Shaking his head like an angry terrier, he wrenched his bill free and hurried back to reassure his mate, leaving the body of the mink to sink languidly to the bottom. Here, among the weeds, it was presently discovered by the eels and crawfish, faithful scavengers, who saw to it that there should be nothing left to pollute the sweet lake-waters.

On the following day the two awkward, dingy-hued, downy chicks were hatched, and thenceforth the parents were kept busy supplying their extremely healthy appetites. The havoc wrought among the finny hordes—the trout and “togue”[1] and chub, the red-fins, shiners, and minnows—was enormous. The loon chicks, enterprising and industrious, speedily learned to help their parents by hunting the small fry in the sunlit shallows along shore.