THE CARE OF YOUNG BIRDS AFTER THEY LEAVE THE NEST
It has been urged as an objection to the Darwinian theory that Natural Selection, if that force exists, must tend to destroy species rather than cause new ones to come into being. Nearly all birds leave the nest before they are fully developed. When they first come out of the nursery they have attained neither their full powers of flight nor complete skill in obtaining food. Every young bird, no matter how fine a specimen it be, leaves the nest an inexperienced weakling, and can therefore stand no chance in competition with the fully grown and experienced members of the species. Natural Selection takes an individual as it finds it and pays no attention to potentialities.
That such an objection should have been urged against the theory of Natural Selection is proof of the fact that naturalists are inclined to forget that, with many, if not all, species of birds, the duties of the parents towards their offspring by no means cease when the young birds leave the nest.
The parent birds, in many cases, continue to feed their young long after these are apparently well able to fend for themselves. This fact is not sufficiently emphasised in books on natural history. On the other hand, such works lay stress upon the fact that in many species of birds the parents drive their offspring away from the place of their birth in order that the numbers of the species in the locality shall not outgrow the food supply. How far this is a general characteristic of birds I do not know. What I desire to emphasise is that the driving-away process, when it occurs, does not take place until some time after the young have left the nest. The fact that the parent birds tend the young long after they have left the nest, and even after they are fully capable of holding their own in the struggle for existence, disposes of the above-cited objection to the theory of Natural Selection. Nature is so careful of the young warriors that she prolongs the instinct of parental affection longer than is absolutely necessary. So important is it that the young should have a fair start in life that she errs on the safe side.
It is common knowledge that foster-parents feed cuckoos when these have grown so large that, in order to reach the mouth of their spurious babes, the little foster-mothers have to perch on their shoulders.
The sight of a tiny bird feeding the great parasite is laughable, but it is also most instructive. It demonstrates how thoroughly bird mothers perform their duties.
Crows tend their young ones for weeks after they have left the nest. I have had ample opportunity of satisfying myself as to this.
It was my custom in Madras to breakfast on the verandah. A number of crows used to assemble daily to watch operations and to pick up the pieces of food thrown to them. They would go farther when the opportunity occurred, and commit petty larceny.
The crows were all grey-necked ones, with the exception of two belonging to the larger black species. But these latter are comparatively shy birds, and consequently used to hang about on the outskirts of the crowd.
Among the grey-necked crows was a family of four -: the parents and two young birds. Every day, without fail, they used to visit the verandah ; the two young birds made more noise than all the rest of the crows put together. They were easily recognisable, firstly, by their more raucous voices, and, secondly, by the pink inside of the mouth. When I first noticed them they were so old that, in size, they were very nearly equal to the mother. Further, the grey of the neck was sharply differentiated from the black portions of the plumage, showing that they had left the nest some time ago.
Unfortunately I did not make a note of the day on which they first put in an appearance. I can, however, safely say that they visited my verandah regularly for some weeks, during the whole of which time the mother bird fed them most assiduously. It was ludicrous to see the great creatures sidle up to mamma when she had seized a piece of toast, and open their red mouths, often pecking at one another out of jealousy.
They were obviously well able to look after themselves; their flight was as powerful as that of the mother bird, yet she treated them as though they were infants, incapable of doing anything for themselves.
At the beginning of the cold weather I changed my quarters, so was not able to witness the break-up of the crow family. Probably this did not occur until the following spring, when nesting operations commenced.
The feeding of the young after they have left the nest and are full-grown is not confined to crows.
I was walking one morning along a shady lane when I noticed on the grass by the roadside a bird which I did not recognise. It was a small creature, clothed in black and white, which tripped along like a wagtail. It had no tail, but it wagged the hind end of its body just as a sandpiper does. While I was trying to identify this strange creature, a young pied wagtail came running up to it with open mouth, into which the first bird popped something. I then saw that the unknown bird was simply a pied wagtail (Motacilla maderaspatensis) which had lost her tail! The young bird was fully as large as the mother, and having a respectable tail, which it wagged in a very sedate manner, looked far more imposing. The parts of the plumage which were black in the mother were brownish grey in the young bird. The white eyebrow was not so well defined in the youngster as in the adult, while the former had rather more white in the wing, but as regards size there was nothing to choose between the two. The young bird remained in close attendance on the mother. It was able to keep pace with her as she dashed after a flying insect. It ran after her begging continually for food. The mother swallowed most of the flies she caught, but now and again put one into the mouth of the young bird, but she did so very severely, as if she were saying, " You are far too old to be fed ; it is no use to pretend you cannot catch insects, you are a naughty, lazy, little bird !" But the lackadaisical air of the young one expressed more plainly than words: " Oh, mother, it tires me to chase insects. They move so fast. I have tried, but have caught so few, and am very hungry."
For several minutes the young wagtail followed the mother; then something arrested its attention, so that it tarried behind its parent. The mother moved away, apparently glad to be rid of the troublesome child for a little. Then she suddenly flew off. Presently the young wagtail looked round for its mother, and I was interested to see what would happen when it noticed that she had flown away. My curiosity was soon satisfied. Directly the young bird perceived that the mother had gone, it set itself most philosophically to catch insects, which it did with all the skill of an old bird, turning, twisting, doubling, with the elegance of an experienced wagtail.
I describe these two little incidents, not as anything wonderful, but as examples of what is continually going on in the world around us.
The parental instinct is probably developed in some birds more than in others, but I believe that in all cases the affection of a bird mother for her young persists long after they have left the nest, and for some time after they are fully capable of looking after themselves.
Birds are born with many instincts, but they have much to learn both before and after they leave the nest.
It is not until their education is complete, until the mother bird has taught them all she herself knows, until they are as strong or stronger than she, that the young birds are driven away and made to look after themselves.