The phalaropes, both the grey and the red-necked species, which are found in Scotland and Ireland, afford a striking example of these unsexed females. Among these birds the rôle of the sexes is reversed. The duties of incubation and rearing the young are conducted entirely by the male, and in correlation with this habit, the female does all the courting. She is stronger and more pugnacious than the male, and is also brighter in plumage. This is really very remarkable. What has acted in bringing about this reversal in the secondary sexual characters? Can the male nature be transferred to the female? These are difficult questions. In colour the phalaropes are a pale olive very thickly spotted and streaked with black. The male is the psychical mother, the female takes no notice of the nest after laying the eggs. Frequently at the beginning of the breeding season she is accompanied by more than one male, so that it is evident polyandry is practised.[30]
The same unusual family conditions prevail with the rhea and the emu, and also among the painted snipes, cassowaries, tinamous, and some of the button-quails.[31] There are probably instances of other birds, but I do not know of details of their habits; Wallace[32] also mentions several species in different parts of the world, among whom all care of the young falls entirely upon the father. In all these bird families exactly opposite conditions prevail to what we are accustomed. It should be specially noted that these unnatural (I use the word simply to mean unusual) mothers are larger and more vividly coloured than the hard-worked fathers; in all such cases polyandry is practised.
Why is this?
The only attempt at an explanation that I have been able to discover is given by Mr. Pycraft in his fascinating book, The Courtship of Animals. He says—[33]
“The solution of this problem probably lies with the physiologist. We now know that the problem of sex does not rest merely in the complete development of the primary sexual organs; we know that fertile unions do not depend merely on the act of pairing, but on the functional activity of the ancillary glands. And it may well be that some change in the character of the secretions has not only affected the numerical values of the sexes, but reversed the normal rôle of coloration and behaviour.”
Mr. Pycraft does not consider that the polyandrous habits of these birds are due primarily to a preponderance of the females in the species over the males, but holds that this condition must rather be regarded as having arisen from a transference to the females, or development in them, of increased sexual hunger, which intensity of passion would tend to lead to an exhaustion of the males. This is exceedingly interesting. Mr. Pycraft continues—
“Neither polygamy nor polyandry among the lower animals, at any rate, has been brought about or is maintained by the excessive death rate due to combats for the possession of mates, but must be explained as demonstrating inherent changes in the germ-plasm, disturbing the relative proportions of the sexes and correlated with a profound transformation, not only in the behaviour of the sexes during the period of reproductive activity, but also in their physical characteristics.”
If I understand this aright, the conclusion seems forced upon us that parental conduct is directly dependent on the action of the sexual appetite: that it may be modified, and in some cases profoundly changed, by any variation in this appetite’s strength and expression. This is of profound interest, and such a view, if established, might explain a great deal.[34] But can it be accepted? To say that such changes are due to the action of the “hormones,” or secretions of the sexual glands, does not help us very much. What we want to know is what induces the changes. There is much that cannot yet be explained. If I may venture to speculate on so difficult a question, it would seem that when the intensity of sex-hunger becomes for any reason stronger in the females than in the males, the result may be a diminishing of the instincts of motherhood. It is as if the egotistic desires of sex were in opposition to the racial duties. This would explain the female phalaropes, whose maternal instincts are completely atrophied. Does it not suggest also a possible explanation of some failures in human motherhood? This opens up questions that reach very far. I am tempted to wait to enlarge on the immense significance of these unnatural bird-mothers in the analogy their conduct bears to one of the most difficult cases of human motherhood—the strongly sexual woman who bears children but is quite unfit and without any desire to rear them. I shall have more to say in the later part of my inquiry about such women, who are driven by passion to be mothers without having any instinct for motherhood.
But now a return must be made to the birds’ nurseries. It is a matter of common knowledge that birds display a marvellous solicitude for the welfare of the young, and their family life presents a beautiful and high standard of conduct.[35] There are very few examples of birds who are bad fathers. Often the male rivals the female in love for the young; he is in constant attendance in the vicinity of the nest; he guards, feeds, and sings to the female, and often shares with her the duty of incubation. The cock ostrich, for example, watches by night over the hole in which the eggs have been buried, and the hen takes this duty by day. The screamer birds, again, work in shifts of two or three hours each. When they bred in the London Zoological Gardens, it was noticed that the cock-bird acted as timekeeper, and at the end of a watch used to come and push the female off the nest.[36] These examples are delightful. It would seem almost that the males, when infected with paternal passion, were more ardent and regular in the performance of nursery duties than the mother.
Among many birds it is usual for all family work to be performed quite irrespective of sex, and the parent who is free takes the task of feeding the one who is occupied with the nest.[37] The male hornbill is a family despot; during the breeding season he walls up his spouse within the trunk of a tree. He feeds her with great care, but he allows her no liberty. As soon as one family is reared many birds at once burden themselves with another. The Californian quail affords an example. In this species the father takes sole charge of the family as soon as the young birds attain the age of three weeks, when the mother begins the labours of rearing a second brood. More curious are the habits of the water hen, among whom the young of the first family assist in the work of feeding their brothers and sisters of the later broods.[38]