Herons are found all over the world, except in the coldest regions, each one of the primary zoogeographical divisions having a fair share, though North America is poorest and South America richest in that respect. We recognize three sub-families,--the bitterns, which have two pairs of powder-down patches only; the true herons, which have three; and the boat-bills, with four pairs. The powder-downs, though present also in some few birds belonging to other orders, are very characteristic of the herons, and many are the speculations which have been indulged in to find out their use to the birds. Some have thought that these patches of dense, clammy, yellowish down may be the cause of the herons being so singularly free of lice and vermin. It has also been hinted at that the old tale of a mysterious light emanating from the heron's bosom when fishing in the dark might have some foundation of fact, and that the powder-down might be the seat of such a light-emitting power.
We shall, in the following, give some extracts of a most excellent account by Mr. W.H. Hudson of the habits of some South American herons; the more since, as he correctly remarks, there is such a sameness in the way of life of these birds that most of what can be said about one species will equally well apply to others.
"Two interesting traits of the heron (and they have a necessary connection) are its tireless watchfulness and its insatiable voracity; for these characters have not, I think, been exaggerated even by the most sensational of ornithologists. In birds of other genera, repletion is invariably followed by a period of listless inactivity, during which no food is taken or required. But the heron digests his food so rapidly that, howsoever much he devours, he is always ready to gorge again; consequently he is not benefited by what he eats, and appears in the same state of semi-starvation when food is abundant as in times of scarcity. An old naturalist has suggested as a reason for this that the heron, from its peculiar manner of taking its prey, requires fair weather to fish; that during spells of bad weather, when it is compelled to suffer the pangs of famine inactive, it contracts a meagre consumptive habit of body which subsequent plenty cannot remove. A pretty theory; but it will not hold water: for in this region spells of bad weather are brief and infrequent; moreover, all other species that feed at the same table with the heron, from the little flitting Ceryle to the towering flamingo, become excessively fat at certain seasons, and are at all times so healthy and vigorous that, compared with them, the heron is but the ghost of a bird. In no extraneous circumstances, but in the organization of the bird itself, must be sought the cause of its anomalous condition. It does not appear to possess the fat-elaborating power; consequently no provision is made for a rainy day, and the misery of the bird consists in its perpetual, never-satisfied craving for food.
"The heron has but one attitude, --motionless watchfulness; so that, when not actually on the wing or taking the few desultory steps it occasionally ventures on, and in whatever situation it may be placed, the level ground, the summit of a tree, or in confinement, it is seen drawn up, motionless, and apparently apathetic. But when we remember that this is the bird's attitude during many hours of the night and day, when it stands still as a reed in the water that in such a posture it sees every shy and swift creature that glances by it, and darts its weapon with unerring aim and lightning rapidity, and with such force that I have seen one drive its beak quite through the body of a fish very much too large for the bird to swallow, and cased in, bony armor, it is impossible not to think that it is observant and keenly sensible of everything going on about it."
The herons are remarkable for their habits of perching and nesting on trees, notwithstanding their long neck and legs, and their 'gressorial' feet. But the length and the low position of the hind toe enables them to live an arboreal life, which seems so incongruous with the rest of their structure. We quote again from Mr. Hudson: "In the variegated heron (Ardetta involucris) [a bittern inhabiting southern South America], the least of the tribe, the perching faculty probably attains its greatest perfection, and is combined with locomotion in a unique and wonderful manner. This little heron frequents beds of reeds growing in rather deep water. Very seldom, and probably only accidentally, does it visit the land; and only when disturbed does it rise above tide reeds, for its flight, unlike that of its congeners, is of the feeblest; but it lives exclusively amongst the reeds, that, smooth as a polished pipe-stem, rise vertically from water too deep for the bird to wade in. Yet the heron goes up to the summit or down to the surface, and moves freely and briskly about amongst them, and runs in a straight line through them almost as rapidly as a plover runs over the bare level ground.
"When driven from its haunt, the bird flies eighty or a hundred yards off, and drops again amongst the rushes; it is difficult to flush it a second time, but a third impossible. And a very curious circumstance is that it also seems quite impossible to find the bird in the spot where it finally settles. This I attributed to the slender figure it makes, and to the color of the plumage so closely resembling that of the withering yellow and spotted reeds always to be found amongst the green ones; but I did not know for many years that the bird possessed a marvellous instinct that made its peculiar conformation and imitative color far more advantageous than they could be of themselves.
"One day in November, 1870, when out shooting, I noticed a little heron stealing off quickly through a bed of rushes, thirty or forty yards from me; he was a foot or so above the ground, and went so rapidly that he appeared' to glide through the rushes without touching them. I fired, but afterwards ascertained that in my hurry I missed my aim. The bird, however, disappeared at the report; and thinking I had killed him, I went to the spot. It was a small isolated bed of rushes I had seen him in; the mud below and for some distance round was quite bare and hard, so that it would have been impossible for the bird to escape without being perceived; and yet, dead or alive, he was not to be found. After vainly searching and re-searching through the rushes for a quarter of an hour, I gave over the quest in great disgust and bewilderment, and, after reloading, was just turning to go, when, behold! there stood my heron as a reed, not more than eight inches from, and on a level with, my knees. He was perched, the body erect and the point of the tail touching the reed grasped by its feet; the long, slender, tapering neck was held stiff, straight, and vertically; and the head and beak, instead of being carried obliquely, were also pointing up. There was not, from the feet to the tip of the beak, a perceptible curve or inequality, but the whole was the figure (the exact counterpart) a straight tapering rush; the loose plumage arranged to fill inequalities, the wings pressed into the hollow sides, made it impossible to see where the body ended and the neck began, or to distinguish head from neck or beak from head. This was, of course, a front view; and the entire under surface of the bird was thus displayed, all of a uniform dull yellow like that of a faded rush. I regarded the bird wonderingly for some time; but not the least motion did it make. I thought it was wounded or paralyzed with fear, and, placing my hand on the point of its beak, forced the head down till it touched the back; when I withdrew my hand, up flew the head, like a steel spring, to its first position. I repeated the experiment many times with the same result, the very eyes of the bird appearing all the time rigid and unwinking like those of a creature in a fit. What wonder that it is so difficult -- almost impossible -- to discover the bird in such an attitude! But how happened it that while repeatedly walking round the bird through the rushes I had not caught sight of the striped back and the broad dark-colored sides? I asked myself this question, and stepped round to get a side view, when, mirabile dictu, I could still see nothing but the rush-like front of the bird! His motions on the perch as he turned slowly or quickly round, still keeping the edge the blade-like body before me, corresponded so exactly with my own that I almost doubted that I had not moved at all. No sooner had I seen the finishing part of this marvellous instinct of self-preservation (this last act making the whole entire), than such a degree of delight and admiration possessed me as I have never before experienced during my researches, much as I have conversed with wild animals in the wilderment, and many and perfect as are the instances of adaptation I have witnessed."
