Animal Intelligence / The International Scientific Series, Vol. XLIV.

by George John Romanes

The following is quoted from Couch ('Illustrations of Instinct,' p. 227 et seq.):—

Mr. Waterton says there is a peculiarity in the nidification of the domestic swan too singular to be passed over without notice. At the time it lays its first egg the nest which it has prepared is of very moderate size; but as incubation proceeds we see it increase vastly in height and breadth. Every soft material, such as pieces of grass and fragments of sedges, is laid hold of by the sitting swan as they float within her reach, and are added to the nest. This work of accumulation is performed by her during the entire period of incubation, be the weather wet or dry, settled or unsettled; and it is perfectly astonishing to see with what assiduity she plies her work of aggrandisement to a nest already sufficient in strength and size to answer every end. My swans generally form their nest on an island quite above the reach of a flood; and still the sitting bird never appears satisfied with the quantity of materials which are provided for her nest. I once gave her two huge bundles of oaten straw, and she performed her work of apparent supererogation by applying the whole of it to her nest, already very large, and not exposed to destruction had the weather become ever so rainy.

This same author continues:—

It is probable that this disposition to accumulation, in its general bearing, has reference to heat rather than the flood; but that the wild swan has a foresight regarding danger, and a quick perception as to the means of securing safety, appears from an instance mentioned by Captain Parry, in his Northern voyage. When everything was deeply involved in ice, the voyagers were obliged to pay much attention to discern whether they were travelling over water or land; but some birds, which formed their nest at no great distance from the ships, were under no mistake in so important a matter; and when the thaw took place it was seen that the nest was situated on an island in the lake.

The following cases are likewise taken from Couch (loc. cit., p. 225):—

This swan was eighteen or nineteen years old, had brought up many broods, and was highly valued by the neighbours. She exhibited, some eight or nine years past, one of the most remarkable powers of instinct ever recorded. She was sitting on four or five eggs, and was observed to be very busy in collecting weeds, grasses, &c., to raise her nest; a farming man was ordered to take down half a load of haulm, with which she most industriously raised her nest and the eggs two feet and a half; that very night there came down a tremendous fall of rain, which flooded all the malt-shops and did great damage. Man made no preparation, the bird did; instinct prevailed over reason. Her eggs were above, and only just above, the water.

During the early part of the summer of 1835, a pair of water-hens built their nest by the margin of the ornamental pond at Bell's Hill, a piece of water of considerable extent, and ordinarily fed by a spring from the height above, but into which the contents of another large pond can occasionally be admitted. This was done while the female was sitting; and as the nest had been built when the water level stood low, the sudden influx of this large body of water from the second pond caused a rise of several inches, so as to threaten the speedy immersion and consequent destruction of the eggs. This the birds seem to have been aware of, and immediately took precautions against so imminent a danger; for when the gardener, upon whose veracity I can safely rely, seeing the sudden rise of the water, went to look after the nest, expecting to find it covered and the eggs destroyed, or at least forsaken by the hen, he observed, whilst at a distance, both birds busily engaged about the brink where the nest was placed; and when near enough he clearly perceived that they were adding, with all possible despatch, fresh materials to raise the fabric beyond the level of the increased contents of the pond; and that the eggs had by some means been removed from the nest by the birds, and were then deposited upon the grass about a foot or more from the margin of the water. He watched them for some time, and saw the nest rapidly increase in height; but I regret to add that he did not remain long enough, fearing he might create alarm, to witness the interesting act of replacing the eggs which must have been effected shortly after; for, upon his return in less than an hour, he found the hen quietly sitting upon them in the newly raised nest. In a few days afterwards the young were hatched, and, as usual, soon quitted the nest and took to the water with their parents. The nest was shown to me in situ shortly after, and I could then plainly discern the formation of the new with the older part of the fabric.

We must not conclude these remarks on nidification without alluding to Mr. Wallace's chapters on the 'Philosophy of Birds' Nests,' in his work on 'Natural Selection.' This writer is inclined to suppose that birds do not build their nests distinctive of their various species by the teachings of hereditary instinct, but by the young birds intelligently observing the construction of the nests in which they are hatched, and purposely imitating this construction when in the following season they have occasion to build nests of their own. With reference to this theory it is only needful to say that it is antecedently improbable, and not well substantiated by facts. It is antecedently improbable because, when any habit has been continued for a number of generations—especially when the habit is of a peculiar and detailed character—the probability is that it has become instinctive; we should have almost as much reason to anticipate that the nest of the little crustacean Podocerus, or the cell of the hive-bee, is constructed by a process of conscious imitation, as that this is the case with the nests of birds. And this theory is not well substantiated by facts because, if the theory were true, we should expect considerable differences to be usually presented by nests of the same species. Unless the construction of the nest of any given species were regulated by a common instinct, numberless idiosyncratic peculiarities would necessarily require to arise, and there would only be a very general uniformity of type presented by the nests of the same species.

A more valuable contribution to the 'Philosophy of Birds' Nests' is furnished by this able naturalist when he directs attention to a certain general correlation between the form of the nest and the colour of the female. For, on reviewing the birds of the world, he certainly makes good the proposition that, as a general rule, liable however to frequent exceptions, dull-coloured females sit on open nests, while those that are conspicuously coloured sit in domed nests. But Mr. Darwin, in a careful review of all the evidence, clearly shows that this interesting fact is to be attributed, not, as Mr. Wallace supposed, to the colour of the female having been determined through natural selection by the form of the nest, but to the reverse process of the form of the nest having been determined by the colour of the female.[170]

Another general fact of interest connected with nidification must not be omitted. This is that the instincts of nidification, although not so variable as the theory of Mr. Wallace would require, are nevertheless highly plastic. The falcon, which usually builds on a cliff, has been known to lay its eggs on the ground in a marsh; the golden eagle sometimes builds in trees or on the ground, while the heron varies its site between trees, cliffs, and open fen.[171] Again, Audubon, in his 'Ornithological Biography,' gives many cases of conspicuous local variations in the nests of the same species in the northern and southern United States; and, as Mr. Wallace truly observes,—