Saruses feed upon vegetable substances, insects, earthworms, frogs, lizards, and other small reptiles, with an occasional snake thrown in by way of condiment. “This,” remarks Babu Ram Brama Sanyal, “shows the kind of accommodation they must have.”
Saruses are not gregarious birds, but hunt in couples and are said to mate for life. It is further asserted that when one of a pair is killed the other pines away and dies. I believe this to be true, although I cannot vouch for it, and am certainly not going to put the statement to the test by shooting one of a pair: for these cranes are such tame, confiding birds that to shoot them savours strongly of murder.
According to Jerdon, a young sarus is not bad eating, but old birds are worthless for the table. Lucky old birds! Saruses thrive very well in captivity. As they habitually indulge in all manner of eccentric dances they make most amusing pets. They are usually gentle and let strangers caress them and tickle their heads. But I always let others try this on for the first time with a strange crane, because some birds resent this head-tickling and, to again quote from the worthy Babu above mentioned, “appear to exist only as it were for pecking at everything, bird, beast, and man: children being the special object of their wrath.”
There are two cranes in the “Zoo” at Lahore; they are a most mischievous couple. They used to be kept with the ducks and geese, and amused themselves by rooting up all freshly planted rushes. At feeding time it was their habit to hop from one dish of food to another with outstretched wings and thus frighten off the ducks and secure the lion’s share for themselves. They were then removed to the enclosure where the adjutants are. They started playing tricks on these, but the adjutant has a powerful beak which he is quite ready to use when necessity arises. The result is that the saruses are not on speaking terms with the adjutants.
Unlike the adjutant, whose nest is a huge platform of sticks placed on the top of a very lofty tree, the sarus builds its nursery on the ground. This takes the form of a large cone, several feet in diameter at the base and two or three feet high. It is composed of reeds, rushes, and straw, and placed by preference in shallow water. Great care is taken to keep the eggs above water level. If, as is apt to happen in India, heavy rain comes on after the completion of the nest, the parents speedily set to work to raise the eggs by adding more material to that upon which they rest.
THE STABILITY OF SPECIES
If two crows be taken to an ornithologist and he be told that one of them was caught in the Himalayas while the other was captured in Madras, he will not be able to tell which individual came from which area: in other words, the crows of Madras resemble those of the Himalayas. This, of course, is no unusual phenomenon. The same may be said of the myna, the king-crow, and a great many other birds and beasts. Yet the phenomenon is a remarkable one if we take into account the facts of variation.
If several hundred thousand crows be collected and carefully examined, it will be found that no two of them resemble one another in all respects. This being so, we should expect the crows of Madras to differ from those of the Himalayas, since the two environments are so dissimilar. We may say with tolerable certainty that no intercrossing takes place between the crows of the two localities: for these birds are stay-at-home creatures, and do not wander far afield. In this case, therefore, it is not intercrossing that has prevented the origin of local races.
A consideration of the main causes which conduce to the stability of species may not be devoid of interest; for the subject is one which has hitherto attracted but little attention. Since the Darwinian hypothesis was given to the world we have heard so much of variation and the origin of new species that the other phenomenon—that of the fixity of species—in spite of varying environments has been almost entirely overlooked. Yet it was just this feature of animal life that attracted the attention of the older zoologists and led them to believe that species had been created once and for all, and that, when created, they were immutably fixed.
Most biologists, if asked to explain the comparative fixity of species, the slowness of evolution, would, I think, refer to the fact that variations appear to take place indiscriminately in all directions. Take, for example, a large number of birds of any species and measure any one organ, let us say the first primary wing feather. Suppose the average length be six inches. We shall find that in a considerable percentage of the individuals measured the wing is exactly six inches in length: that six inches is what we may call the favourite or fashionable length of the wing. The next commonest lengths will be 5.99 and 6.01 inches, and so on. We shall find that only a very small percentage of the individuals have wings shorter than 5½ inches or longer than 6½ inches; and if we measured a thousand individuals we probably should not find any in which the wing was shorter than five inches or longer than seven.