The Bald Eagle of North America (_Haliaeetus leucocephalus_) hides himself on a rock by the edge of a stream and awaits the passing of a swan. This eagle is brave and strong, but the palmiped is vigorous, and though inferior in the air, he has an advantage on the water, and may escape death by plunging. The eagle knows this advantage, so he compels the swan to remain in the air by attacking him from below and repeatedly striking his belly. Weakened by the flow of blood, and obliged to fly, not being able to reach the water without finding the sharp beak which strikes him, the swan succumbs in this unequal combat, which has been vividly described by Audubon. [Illustration: FIG. 4.] The bird who displays the most remarkable qualities in this struggle which terminates the chase, exhibiting indeed a real fencing match, is the Secretary Bird (_Gypogeranus reptilivorus_. Fig. 4.) He is the more interested in striking without being himself struck since the fangs with which his prey, the snake, is generally armed might at the first blow give him a mortal wound. In South Africa he pursues every snake, even the most venomous. Warned by instinct of the terrible enemy he has met, the reptile at first seeks safety in flight; the Secretary follows him on foot, and the ardour of the chase does not prevent him from being constantly on guard. This is because the snake, finding himself nearly overtaken, suddenly turns round, ready to use his defensive weapons. The bird stops, and turns in one of his wings to protect the lower parts of his body. A real duel then begins. The snake throws himself on his enemy, who at each stroke parries with the end of his wing; the fangs are buried in the great feathers which terminate it, and there leave their poison without producing any effect. All this time with the other wing the Secretary repeatedly strikes the reptile, who is at last stunned, and rolls over on the earth. The conqueror rapidly thrusts his beak into his skull, throws his victim into the air, and swallows him.[20] [20] The combat was minutely described by Le Vaillant (_Hist. Nat. des Oiseaux d'Afrique_, Paris, 1798, t. i. p. 177), whose account has been confirmed by many subsequent observers. [Illustration: FIG. 5.]