All eagles are monogamous. Golden eagles live in couples and remain attached to one another for a hundred or more years, without even changing their domicile.[54] The conjugal unions of bald-headed eagles, although they are under no “legal restrictions,” last until the death of one of the partners. Among birds, although incubation rests with the mother, the father usually assists his companion. He not only takes her place if she desires to leave the nest for a moment, but also provides her with food.[55] So perfect is the bird family life that Brehm declares that “real genuine marriage can only be found among birds.”[56] Upon this subject we are informed that “examples of wandering fancy are for the most part rare among the birds, the majority of whom are monogamous, and even superior to most men in the matter of conjugal fidelity.”[57] [54] J. G. Wood, _Natural History_, p. 262. [55] Westermarck, _The History of Human Marriage_, p. 11. [56] Brehm, _Bird-Life_. [57] Letourneau, _The Evolution of Marriage and the Family_, p. 27. Concerning mammals, it is observed that although polygamy is frequent “it is far from being the conjugal regime universally adopted; monogamy is common, and is sometimes accompanied by so much devotion that it would serve as an example to human monogamists.”[58] Bears, weasels, whales, and many other animals choose their mates and go in pairs. Several kinds of monkeys are strictly monogamous.[59] Chimpanzees are sometimes polygamous and sometimes monogamous. It is stated what when a strong male has succeeded in driving away the other males of the group, the females, although in a position to subjugate him, are nevertheless kind and even tender toward him. They are doubtless too much occupied with their legitimate functions to rebel, but so soon as the young of the horde are grown, the usurper is driven from their midst. A little observation will show us that even among polygamous species, it is affection rather than strength which keeps the members of a group together. Although among most of the lower orders the female exercises a choice in the selection of her mate, still among animals of polygamous habits the female is said to manifest genuine affection for the father of her offspring. [58] _Ibid._, p. 35. [59] Darwin, _The Descent of Man_, p. 590. The polygamic regime of animals is far from extinguishing affectionate sentiments in the females towards their husband and master. The females of the guanaco lamas, for example, are very faithful to their male. If the latter happens to be wounded or killed, instead of running away, they hasten to his side, bleating and offering themselves to the shots of the hunter in order to shield him, while, on the contrary, if a female is killed, the male makes off with all his troop; he only thinks of himself.[60] [60] Letourneau, _The Evolution of Marriage and the Family_, p. 32.