[Published in 1927: Smithsonian Institution United States National Museum Bulletin 135: 197-213]
The familiar night heron or "quawk" is one of the best known and most widely distributed of our herons. Closely related forms of the same species are found throughout much of South America, Europe, Asia, and Africa. Throughout its wide North American range it is practically homogenous. It is decidedly different in many ways from our other herons; its short, stout figure is easily recognized; and it well deserves the name of night heron. How often, in the gathering dusk of evening, have we heard its loud, choking squawk and, looking up, have seen its stocky form, dimly outlined against the gray sky and propelled by steady wing beats, as it wings its way high in the air towards its evening feeding place in some distant pond or marsh! And how often, as we walked along the reedy border of some marshy creek or pond hole, have we been startled by its croak of alarm, as it rose unexpectedly from behind the reeds and flew deliberately away, a wide band of black supported by broad gray wings! The young birds are particularly unsuspicious in such situations and often spring up almost under our feet; their peculiar shape and speckled plumage are easily recognized.
The name, night heron, immediately suggests to my mind Sandy Neck and the famous rookery that has flourished and struggled alternately for over a century on that long chain of sand dunes that separates Barnstable Harbor from Cape Cod Bay. Many ornithologists have visited it and I have seen it many times in spring, summer, autumn, and winter. Several times it has been "shot out" and it has, within my memory, occupied three different parts of the neck a mile or more apart. Sandy Neck is about 6 miles long. Its northern or bay side is the continuation of a broad, flat, sandy beach, which extends for many miles along the north side of Cape Cod and terminates in a wide point of bare sand. On its southern or harbor side it is bordered by extensive salt meadows or marshes, covering several square miles and intersected by numerous creeks, channels, and ditches. The central portion consists of a series of picturesque sand dunes, some low and rolling hillocks and some high mountains of sand with steep sides and narrow crests, from which one may gain a comprehensive view of the long succession of barren, wind-swept peaks, protecting sheltered hollows filled with luxuriant vegetation. Some of the older hills are heavily wooded with oaks, pitch pines, maples, sassafras, and wild cherries, beneath which are often impenetrable thickets of scrub oak, alder, sumac, and other underbrush, interwoven with tangles of cat-briar, woodbine, and poison ivy. There are also numerous clusters of beach plums and bayberry bushes in the hollows or on the sand dunes and several small cranberry bogs and swampy pond holes. Altogether it is an ideal location for a heron rookery, with plenty of suitable nesting sites in secluded spots and with abundant food supplies, on the broad sand flats off the beaches, along the many miles of tidal creeks on the marshes, and around the marshy pond holes and bogs in the hollows. Here the largest colony of night herons, at least the largest of which I can find any record, in North America makes its summer home.
Courtship.--On April 30, 1924, I made a special trip to the Barnstable rookery to study the courtship of this heron. I found the breeding season well under way; many nests were in process of construction and some already held from one to three eggs. The birds were rather shy, but several times I was able to observe the rather simple courtship ceremony. The male alights in the tree top beside the female, or a little above her; he bows low, leaning down toward her, erecting his crest and the feathers of his neck, breast, and back in a rather striking display; she responds in much the same way; their red eyes glow with sexual excitement; they caress each other with their bills and then assume a quiet pose, side by side, the plumage as smooth as usual. Or perhaps the female alights in a tree where the male is standing; with plumage erected, she courts his attention with a squawk of invitation; he responds in the same manner, comes to her and mounts her, holding her head with his beak, spreading his wings and erecting his plumage. Thus the conjugal pact is sealed. If another male alights near them, the female urges her spouse to drive him away; and he does so, with much squawking and ruffling of plumage, and with many savage bill strokes and wing blows.
Similar plumage displays are seen all through the breeding season, in this as in all the other herons, as mutual greetings, in the ceremony of nest relief and when feeding the young. They seem to be expressions of love or sexual emotion.
Nesting.--My acquaintance with the Barnstable rookery began in 1897. It then occupied a heavily wooded area near the southern edge of the sand hills; the center of abundance seemed to be in a large deep hollow where the red oak, sassafras, and maple trees grew to a height of 25 or 30 feet. I remember standing in this hollow one day in the winter when the leaves were off, and counting 275 nests in sight from one spot. The herons were still occupying the same nesting site in 1908, but the colony had increased greatly in size; my impression was that it had nearly doubled, and it had spread out over a much larger area, nearly half a mile long and an eighth of a mile wide. The nests were placed in pitch pines, red oaks, maples, scrub oaks, and sassafras, mainly in the oaks, often two or three nests in a tree and sometimes as many as four or five. The so-called sportsmen of the neighborhood found the herons useful as targets on which to practice, and their constant persecution forced the herons to move to a new nesting site about a mile farther out on the neck. Here we found them in 1910, occupying a mixed tract of pitch pines and oaks on the borders of a cranberry bog in a hollow among the sand dunes. We estimated that the colony contained from 1,500 to 2,000 pairs of herons. The main portion of the colony was closely concentrated in a grove of small pitch pines, from 15 to 20 feet high, with a dense undergrowth of scrub oak and an almost impenetrable tangle of cat brier and other vines.
Three years later, in 1913, we found that the colony had moved again and was located still farther out on the neck, near the extreme end of the wooded areas, in an extensive grove of pitch pines, with comparatively few oaks. Here it has remained ever since and is still in a flourishing condition. During the summer of 1920, Dr. Alfred O. Gross (1923) camped on the neck for two months and made an intensive study of these birds; the published results of his exhaustive study would make an excellent life history of this species. I shall use his data freely, but would refer the reader to his excellent paper for many details which space will not permit me to publish. On June 22 and 23 he made a detailed census of the rookery, marking each tree as it was counted and recording the number of nests in each. The count showed 2,536 nests in 854 trees, the largest number of trees, 282, contained only 1 nest each; and the largest numbers of nests were recorded in 13 trees which held 8 nests each, 5 trees which held 11 nests and 1 tree each which held 13 and 14 nests, respectively.
About 90 percent of the nests of this colony were built in low pitch pines and the remainder were in scrub oaks, maples, and a few in the bayberry and alder bushes which grew in the lower swampy portions of the grove. The height of the nests varied from one in a bayberry bush 2 feet above the water to one 42 feet high in one of the larger pines. The average height of 100 nests, which were carefully measured, was 22 feet, four inches. These nests, unlike those in the spruce groves of Maine, were generally located on the forked tips of the large branches and a considerable distance from the main trunk of the tree.
The nests in this rookery vary greatly in size, stability, and composition. Many of them are crude, loosely-built platforms, made of coarse sticks, and scantily lined with finer twigs. Some are so small and so insecurely placed that the eggs or young are shaken out of them by heavy winds and the nests are blown out of the trees during the winter storms. Others are large, well-built structures, securely located in some firm crotch or supported by two or three flat branches; such nests usually survive the winter storms and are used year after year. These better types of nests consist of substantial foundations of sticks and twigs of pine, oak, beach plum, and bayberry, lined with fine twigs, roots, vines, grasses, and pine needles. Doctor Gross (1923) says:
A large percentage of the nests were lined in part or wholly with the long flexible roots of beach grass. It puzzled me to know how it were possible for the birds to secure some of the very long roots, some of which were more than a meter in length, until I chanced upon a score of adult herons tugging at the roots which had been left unearthed in the wake of a traveling sand dune. The numerous footprints in the sand evidenced that such places were the common source of their supply. The roots provided an unusual but admirable nesting material and some of the nests lined with them represented the finest types built by the herons at Sandy Neck. Both the male and the female actively concern themselves in the work of building the nest which usually requires from two to five days, but, in the case of one nest, construction work and alterations were going on for a period of more than a week.
A rookery quite similar to the Sandy Neck colony, formerly located on Plum Island, Massachusetts, is well described by S. Waldo Bailey (1915). On July 5, 1903, I examined a fair-sized colony on Cappaquiddic Island, adjoining Martha's Vineyard; the rookery was located on the highest land in the center of the island in an extensive tract of dry woods, principally black and red oaks with some sassafras and beech; the nests were all in the oaks from 7 to 15 feet from the ground. On June 8, 1919, I found a colony of from 200 to 300 pairs, probably the same colony, nesting in an extensive patch of low cedars near the shore, a mile or more away; even at that date most of the nests contained young, some of which were fully grown and were climbing out on the branches. Dr. Charles W. Townsend showed me, on July 19, 1913, a somewhat different type of rookery in Hamilton, Massachusetts, which he had previously described; it was in a mixed swamp of larches, black spruces, white pines, and maples in which the nests were from 20 to 30 feet up; the young were nearly all on the wing, but there were still a few in the nests.
I have seen several night heron rookeries on the coast of Maine, where this species nests in colonies by itself or in company with the great blue heron. Referring to some of these colonies Doctor Gross (1923) says:
In Maine, spruce-covered islands or dense groves of conifers on the mainland near the salt water are the places where one is most likely to meet with success in locating the largest breeding places and roosts. Mr. A. H. Norton of the Portland Natural History Society visited Allens Island in June, 1921, and found a rookery comprising about 100 great blue herons, and nearly 400 black-crowned night herons. The nests on Allens Island were built at an average height of 25 feet in the low spruce trees which there do not exceed 30 to 40 feet in height. The majority of the nests were supported by the lower branches of the green conical tops so that they were in plain view to an observer standing on the forest floor. Several ravens were seen at this colony and Mr. Norton thinks some of the dead half-eaten young that were lying on the ground represented the work of these black marauders. The colony at Whaleboat Island which contained only 30 pairs of herons in 1915 has increased to a thriving community of more than 250 birds, not including about 50 great blue herons which regularly nest there. The nests seen here were without exception built in the tall dead spruces, those of the night heron at an average height of 34 feet from the ground. None of them were lower than 10 feet and one was built near the top of a tall spruce more than 60 feet in height. At this place there seemed to be a rough correlation between the height of the trees and the position of the nest. The majority of the nests were nearly the same distance from the top of the respective trees, a place where the densely branched limbs were best adapted for holding the nest. They were built near the trunk and were usually supported by the bases and smaller lateral branches of two or more horizontal limbs.
In other parts of the country night herons nest under widely different conditions. Where suitable trees cannot be found in favorable localities the herons are often found breeding in marshes or sloughs, where their nests are concealed in some secluded spot. Robert B. Rockwell (1910) found a particularly interesting colony of this type near Barr, Colorado, of which he writes:
As we approached the spot where the colony was supposed to be located, not a sign of the birds was to be seen--save the monotonous expanse of cat-tail marsh, flanked by a small rush-bound lake on one side and the sunburned prairie on the other. We had worked well into the cat-tails, which towered some distance above our heads, when as if by a given signal the breeding birds rose from their nests in a cloud, and with much squawking, scolding, and flapping of wings, rapidly retreated to a place of safety in the marsh half a mile or more distant. Fifty yards farther on we came to the spot from which the birds had risen, and here in the dense cat-tails were the nests, probably 150 in all, large, clumsy, yet withal well built structures of coarse sticks and weed stalks, ranging in height from 6 inches to 3 feet above the ground, which was wet and boggy and in many places covered with several inches of water. On May 11, while working over a small lake about a half mile below the marsh which harbored the nesting colony of the preceding year, we found two nests of these erratic birds, built just above the surface of water almost waist deep and fully 50 yards out from the shore of the lake. These nests--the bottoms of which were just level with the surface of the water--were supported by masses of floating, dead vegetation, and were anchored in place by a few upright dead cat-tail stalks. They were beautifully built affairs of slender twigs and weed stalks, very large, bulky, deeply cupped and quite symmetrical; and lying far out from shore upon the open water they were very conspicuous, being easily discernible at a distance of 100 yards. The parent birds were very wild, and it was impossible to approach anywhere near the nests without flushing the birds.
In Florida we often found black-crowned night herons nesting in small numbers in the rookeries with other herons. Many of the rookeries examined on the coast of Texas contained a few pairs of this species, nesting in low situations in the shrubbery. On one island, in Galveston Bay, they were nesting in tall canes, where their nests were made wholly of the stems of dead canes. On Dressing Point Island, in Matagorda Bay, we found a fair-sized colony nesting on the dry ground among tufts of tall grass.
Doctor Gross (1923) refers to a number of different colonies nesting in a variety of situations, among which he mentions a colony which "selected an old apple orchard for their nesting site," which they occupied for 10 years, near Atwood, Illinois.
W. L. Finley (1906) found a colony of about 200 pairs in a fir forest south of Portland, Oregon, in which none of the nests were less than 130 feet up and some were 160 feet above the ground. In a colony which he found at the lower end of San Francisco Bay, California, in the summer of 1904, he noted 41 nests of the great blue heron and 28 nests of the black-crowned night heron in a single giant sycamore, 7 feet thick at the base, 120 feet high and with a spread equal to its height. In another tree there were 17 great blue and 28 night heron nests. In this large colony of 700 nests those of the night heron were placed at the very upturned tips of the sycamore limbs or else in the willows and alders at a relatively short distance from the ground. Mr. Finley counted 400 eggs from a single point in a giant sycamore tree which gives some idea of the density of the heron homes at this unusual rookery. In other localities in California, such as Merced and San Diego Counties, night herons have also been found nesting in tule swamps, sometimes in company with white-faced glossy ibises.
Eggs.--This night heron usually lays from three to five eggs, sometimes only two or even one, occasionally six and very rarely seven or even eight; the larger sets may be the product of two birds. In shape they vary from ovate or oval to cylindrical ovate. The shell is smooth with no gloss. The color is pale bluish green, varying from "glaucous green" to "pale flourite green."
The measurements of 48 eggs average 51.5 by 37 millimeters; the eggs showing the four extremes measure 58 by 35.5, 50 by 39.5, 48 by 35.5 millimeters.
Young.--Doctor Gross (1923) found that the period of incubation varied from 24 to 26 days and that both sexes take an active part in it; he "frequently had nests under observation when the shift from one sex to the other took place. Sometimes the shift involved a domestic quarrel in which there resulted a vigorous interchange of sharp, rebuffing shrieks accompanied by violent thrusts." He says it is customary to start incubation after the first egg is laid, although it may take a week to complete the set; this accounts for the inequality in the sizes of the young. He describes the hatching process in detail; a young bird which had pipped the shell at noon was not entirely free from it until 4:20 p.m. the next day.
Young night herons are fed by their parents until they are large enough to learn to fly and fish for themselves. Doctor Gross (1923) says:
The first food received by the downy young consist of juices of predigested material. In the examination made at Sandy Neck, this food was so completely liquefied that it was practically impossible to determine the kind of animals composing it. In delivering the food to the downy young the adult seemed to insert the tip of her beak into the wide open mouth and the transference of the juices was made with comparatively little effort. The parent bird usually delivers small amounts at rather short intervals and I have frequently seen, from my blind, the downy heads of day old birds appear between the feathers of the parent to receive their ration of fish extract. By the third day, more substantial food, such as semidigested fish and shrimp, were given to the young. Among 20 regurgitations of nestlings 3 to 10 days old 16 were made up entirely or largely of shrimps present in pieces ranging from a few millimeters to one and in some instances three centimeters in length. When the young became more than three weeks old the food was made up chiefly of fish, which were often delivered without any predigestion.
I have several times watched the old birds feeding their young; the method varies with the ages of the young. The old bird approaches cautiously, climbing over the branches towards the nest and giving a few warning calls, soft guttural croaks, at which the young rise up in eager anticipation, or, if they are large enough, scramble over the branches toward her; she may keep them waiting for several minutes, but, when ready to feed them, she raises here crest, fluffs out her plumage, half spreads her wings and lowers her head to regurgitate the food. If the young are small, she inserts her bill into the mouth of the little one and pours into it the liquid, semidigested food; if the young are older they may seize the parent's bill and struggle with her until she delivers a good sized fish; sometimes the food is too large to be swallowed entirely and the tail is left protruding from the young bird's mouth until the lower end of it is digested. Often, with large young, the fish is deposited on the nest to be picked up, which frequently results in its falling to the ground and adding to the delightful odors of the rookery. The young have a very bad habit of voiding their excrement and vomiting the contents of their crops, when frightened; the investigator is quite likely to receive some very unpleasant shower baths under such circumstances. It would be well for the observer to wear an old hat and an old suit of clothes, which can be thrown away or better still a complete suit of oilskins or overalls, which can be washed as soon as he comes out of the rookery, else he may carry home some unpleasant reminders.
Provided one can stand the nauseating odors or does not mind the filth, the briars and the insect pests, flies, mosquitos, and wood ticks, it is an exceedingly interesting experience to visit the Sandy Neck rookery in July. As he climbs to the crest of some commanding sand dune, he looks down upon a broad expanse of pines, mingled with oaks and thickets of underbrush and vines. The scene becomes a lively one, as hundreds of the gray, black-backed birds rise in great clouds, circle over the rookery in a bewildering maze and then drift away to settle in the tops of distant trees. The tops of the trees in the rookery are dotted with hundreds of young birds in the brown juvenal plumage, clearly outlined against the dark green of the pines; they are not yet able to fly but have climbed up out of the nests to bask in the sunshine and see the outside world. As he walks down into the rookery the excitement increases, the air is full of birds overheard, the trees are full of scrambling and fluttering young and the din of many voices adds to the pandemonium; the shrill piping notes of the youngest birds, the "yip, yip, yip," or the "yak, yak, yak" of the older young, and the various croaks and squawks of the adults create a volume of sound that is not soon forgotten. Alexander Wilson (1832) has well likened it to 200 or 300 Indians choking or throttling each other.
The young birds remain in the nest, where their parents brood them, or stand over them with wings partly spread to protect them from the sun, until they are two or three weeks old; I believe that they would remain in the nests a week or two longer, if they were left undisturbed. But at the age of two or three weeks, or when about half or two-thirds grown, they are easily frightened from their nests and climb out on the branches or even scramble and flutter from tree to tree. They are awkward and ludicrous in appearance, but they are usually quite successful in their efforts and more expert at climbing than they appear to be. They make good use of all five of their extremities in climbing, clinging with their feet, supporting themselves on their wings, hooking the neck over a branch or seizing it with the bill. I have seen one do what we used to call the "giant swing," clinging to a branch with bill and feet. But, even with all these safeguards and aids to climbing, accidents sometimes happen and I have seen many a dead young heron, hanging by wing or foot, where it was caught and was unable to free itself. Often one falls to the ground where its parents cannot find it, where it must starve unless some prowling fox or cat finds it and ends its misery.
Plumages.--The small downy young of this heron is partially covered on the upper parts with long soft down, varying in color from "dark mouse gray" to "deep neutral gray"; the crown is covered with long, rather coarse, whitish filaments an inch or more long; the under parts are covered more sparsely with soft down, varying from "dark mouse gray" on the neck to "pallid neutral gray" on the belly. These colors all fade out paler with advancing age.
Doctor Gross (1923) has described the development of the juvenal plumages, as follows:
The first papillae of the juvenal plumage make their appearance in the region of the flanks and scapulars on the fifth or sixth day after hatching. These are closely followed by the papillae of the wing coverts and of the ventral tracts. By the seventh day the papillae of the alar tracts (primaries and secondaries) show through the integument but those of the rectrices (tail) do not appear until the bird is about 10 days old. At this age the tips of the feathers of the scapular region and flanks are unsheathed. The primaries and secondaries present their unsheathed tips about the fifteenth day, but no unsheathing takes place in the rectrices until the bird is about three weeks old. The unsheathing when once started proceeds rapidly and by the time the bird is four weeks old it has the smooth contour possessed by an adult bird. The complete growth of the juvenal plumage is not accomplished, however, until the bird is about 50 days old.
He describes the juvenal plumage, of an unfaded specimen 28 days old, as follows:
Crown and back glossy olivaceous black, neck Chaetura drab, the feathers with median streaks of varying shades of buff. The median streaks in the feathers of the back are of a richer and deeper color approaching very nearly that of cinnamon. The apices of the crown feathers have filaments of natal down but the remainder of the juvenal plumage is entirely free of vestiges of this first plumage. The throat with an elongated median patch of white tinged with ivory yellow which extends posteriorly to the neck. Sides of chin, head and neck streaked with Chaetura drab, fuscous-black, and various shades of buff. Feathers of the breast, upper belly, and flanks white tinged with light cartridge buff, each feather with broad lateral streaks or bands of light fuscous or hair brown. Lower belly and crissum white and not streaked. Tail feathers deep mouse gray, primaries and secondaries fuscous black, tipped with white and with outer veins tinged with cinnamon. The white tips of the secondaries are much reduced and the outer veins have less of the cinnamon than have the primaries. The feathers comprising the wing coverts and tertials have large conspicuous terminal spots of white or light buff.
I have several young birds in my collection in which the colors are richer and more rufous than those described above; the feathers of the mantle are largely "auburn" and "hazel" and the buffy central streaks and tips are "ochraceous buff." However, these colors soon fade; in one bird, taken in July, the streaks and spots have all faded out to white and there is no rufous anywhere and very little pale buff. This plumage is worn until the middle of winter or later. The molt into the first nuptial plumage begins in January with the acquisition of clear brown plumage in the back, varying in color from "bister" to "snuff brown," which gradually replaces the streaked and spotted juvenal plumage; this molt spreads during the spring until the entire mantle, back scapulars, and wing-coverts, become clear, dark, rich brown, with a purplish or greenish gloss when fresh; the crown becomes much darker, "clove brown"; the streaking becomes less conspicuous on the sides of the head and neck; and the breast and belly become clearer gray and white, with hardly any signs of streaking; the tail is molted, in April or May, in which the new feathers are clear drab; but the wings are not molted until July or August. There is great individual variation in the time and progress of this prolonged molt.
Almost continuous with the above molt, beginning in July. or even earlier in some individuals, comes the first complete postnuptial molt. This produces, by September or later, a second winter plumage, in which the crown is glossy, greenish black and the mantle becomes "mouse gray," darkest on the back, with a greenish gloss. During the late winter or early spring, a partial prenuptial molt, involving only the contour plumage, produces a second nuptial plumage, which is nearly adult; but the white space in the forehead is washed with drab, instead of being clear white; the black areas of the crown and back are less brilliantly glossed; the wings are darker and more brownish gray, "mouse gray" or "neutral gray"; and there is much more gray in the neck and breast, "light drab" to "drab-gray." One or two of the long, slender white occipital plumes are acquired at this time. At the next postnuptial, complete molt, which begins usually in June or July and lasts sometimes until December, the young bird assumes the fully adult plumage, when about 2 1/2 years old.
Adults have a partial prenuptial molt, in late winter or early spring, and a complete postnuptial molt from August to October. In the spring adult the forehead is pure white; the crown, and particularly the back, are brilliantly glossed with green; the wings are "pale mouse gray" or "pallid mouse gray"; and the neck and underparts vary from "pallid mouse gray" to pure white. The white occipital plumes are often present in the fall, but less highly developed.
Food.--As its name implies, the night heron feeds largely at night, or during the dusk of evening and before sunrise. It is a common experience to hear its familiar croaking notes, as it flies overhead during the evening to or from its feeding grounds. During the nesting season, when the young demand an extra amount of food, it is necessary for their parents to spend more time in search of food and they are kept busy all day and probably most of the night. But the night heron is by no means wholly nocturnal in its feeding habits at any season. It may be flushed at any time during the day, even late in the fall from favorable feeding grounds around the marshy borders of ponds or along the reedy banks of streams. On the seacoast it is largely influenced by the tides and may be seen at low tide out on the mud flats or around the fish weirs; and it knows at just what stages of the tides it can fish to best advantage in the shallows of the tidal creeks.
Audubon (1840) says that "it is never seen standing motionless, waiting for its prey, like the true herons, but it is constantly moving about in search of it." This active method may be the one employed when in search of the less active aquatic animals on which it feeds; but when fishing, I believe, it usually stands still, in shallow water, on the shore, or on some convenient perch. I once saw a young night heron given a lesson in still fishing by, presumably, one of its parents. Both birds had been standing motionless as statues, for some time in the shallow water of a tidal creek; the young bird began to show its impatience by moving its head slightly from side to side; then it took a few steps forward, slowly and stealthily, with its neck stretched out and crouching close to the water; whereupon the adult, which had stood immovable, flew at the young bird, with loud, scolding croaks, and struck it some hard blows on the back with its bill. The young bird was forced to fly, but it settled again a few yards away and did not attempt to move again; perhaps it had learned its lesson.
Doctor Gross (1923) determined that at Sandy Neck about 80 percent of the night herons' food consists of fish, the commonest species being "whiting (Merlucceus bilinearis), herring (Clupea harengus), and cunners (Tantogolabrus adspersus)." Many of the whiting and some other fishes were picked up dead on the beaches. Among other fish taken were a few small flounders, an occasional mackerel and even sculpins, sea robins, and puffers. Many of these were taken from the fish weirs. Other kinds of fish, such as perch, carp, pickerel, and eels, have been reported by other observers. Probably fish constitute the bulk of the food everywhere and whatever species are easily available are taken.
Dr. Alexander Wetmore (1920) observed that, at Lake Burford, New Mexico, the night herons fed on waterdogs (Ambystoma) and frogs, where they acted as scavengers by eating the dead Axolotls which they found floating on the water. Doctor Gross (1923) says:
The remains of animals in the food which could be identified comprised marine annelids, chiefly Nereis virens, crustaceans, represented by numerous shrimp, sand-hoppers, and a few small crabs; insects, chiefly beetles, flies, and dragon-fly nymphs, all present in negligible quantities.
Of the mollusks he found only squids, which were probably picked up dead; and the only fresh water animals found were tadpoles and adults of Fowler's toad. Oscar E. Baynard (1912) found that 50 meals of young night herons in Florida consisted of 60 crayfish, 610 small catfish, 31 small pickerel, and 79 dragon flies. R. P. Sharples wrote me that he found in the stomachs of this species a frog and a snake about a foot long. Other observers have also noted crabs, lizards, salamanders, leeches, moths, and even mice. Doctor Gross (1923) refers to a case, reported by Mr. S. F. Denton, "in which a partly fledged young swallowed a downy nestling which had been placed in the same cage." Referring to vegetable food, which is seldom eaten, he cites authorities to show that sea lettuce, algae, and similar aquatic plants are sometimes eaten and fed to the young.
Behavior.--The flight of the night heron is very different from that of the other herons; in flight and in appearance on the wing it is more like a gull than a heron. It holds itself much like a gull or a crow; its neck is shortened, but not folded back in true heron fashion; and its appearance is that of a short, stout bird. Its flight is strong, direct, and swifter than that of other herons, with usually quicker wing strokes. Sometimes it flies with the graceful ease of a large gull and sometimes it soars or scales almost as well as a hawk; often it sets its wings and scales down into the tree tops or onto the ground. When not too busy with its search for food, it spends much time, especially during the middle of the day, in idleness, perched on some tree or on the shore in its characteristic pose, a short necked, round shouldered bird. Its periods of greatest activity are from dawn till sunrise and from a little before sunset until after darkness has settled; but it is never quiet, day or night, in a night heron rookery.
The characteristic note of the night heron is well expressed in its popular names. Doctor Gross (1923) notes variations which may be crudely represented by "Qua," Quak," "Quark," or "Squawk." He has described the varied vocabulary of the species so well that I cannot do better than to quote his words as follows:
When one approaches the colony he invariably disturbs first the outpost sentinels who seem ever ready to give a warning note which sounds like, "Woc, woc, wock! a-woc, woc, woc." This call usually results in a number of herons rising from the neighboring tree tops, who take up the call and repeat it until a virtual cloud of birds is flying about in great confusion. After you have entered the rookery, the notes of the adults are drowned out by the incessant clatter of the young birds which during July and August are represented by birds of all ages. The call of the downy young resembles a faint "Tet! tet! tet! or "Yip-yip-yip"; the half-grown nestlings utter a sound more like "Yak! yak! yak!" and the older young utter a harsher, coarser sound resembling roughly the words "Chuck, chuck-a-chuck, chuck, chuck." The various calls of the young all mingled together sound like the deafening clatter and hum of an infinite number of machines in a great factory, and, indeed, it is a heron factory. During the course of the day the intensity of the calls of the young varies directly as the keenness of their appetites. These calls could be heard at all hours of the day or night, but just before the bulk of the adult birds came in from the feeding grounds, a time which varied with the tide, the number of young calling and the volume of the sound was at a maximum. At such times the rookery resounded with a deafening monotonous clatter. When the young were hungry, they were also irritable, and the least disturbance by a neighbor would cause them to render a defensive thrust accompanied by a ghastly, sharp accepted "Sque-e-e-e-e-e-ak." In uttering this squeal the beak is thrown wide open, during the "Sque-e-e-e-e-e" and then suddenly snapped together at the termination of the much accented "ak." Doubtless it is these weird sounds which have led some observers to compare the noises of a colony of night herons to the war whoops of a band of Indians.
A similar note is uttered by adults when they are defending their nests against intruders. When the parent bird arrives with food she often utters a series of low guttural tones, some of which resemble very much the sounds made by an old hen when she is brooding her chicks. At other times, she would give a series of loud calls resembling "Oc-oc-goc-goc-goc-oc, oc-oc-oc" or "Woc-a-woc, woc, woc, Wock-a-woc, woc," which, judging from the actions of the young, conveyed a definite unmistakable meaning.
Crows, hawks, and vultures torment the birds by day, while raccoons and other animals destroy them by night. The young are quite as good for eating as those of the common pigeon, being tender, juicy, and fat, with very little of the fishy taste of many birds which, like them, feed on fishes and reptiles. In the neighborhood of New Orleans, and along the Mississippi as far up as Natchez, the shooting of this species is a favorite occupation with the planters, who represent it as equaling any other bird in the delicacy of its flesh.
Grackles often nest in or near the rookeries and may do some damage to the eggs. Ravens are destructive in the Maine rookeries. Foxes are very common on Sandy Neck and probably pick up many young birds that have fallen from nests; Doctor Gross saw one in the rookery one night. Undoubtedly nest-robbing crows are the worst enemies of all herons.
Fall.--Young night herons, like the young of several other herons, are somewhat inclined to wander northward after the close of the breeding season. By September first, or soon after that, the Sandy Neck rookery is practically deserted, the herons having scattered in all directions, either to find new feeding grounds or to satisfy the lust for wandering, and the same seems to be true of the other rookeries. Systematic bird banding has thrown considerable light on this subject and given us a number of positive records, some of which Doctor Gross (1923) has published. Young birds, banded at Sandy Neck, have been taken at Goat Island, Maine, 120 miles north, at Seabrook, New Hampshire, 90 miles northwest, at Kennebunkport, Maine, and at Fryeburg, Maine, 200 miles north. Birds banded by Dr. Paul Bartsch, near Washington, D. C., were taken at Abington, Maryland, at Pennsville, New Jersey, and at Leesburg, Virginia. Herons banded by Dr. John C. Phillips, at Wenham, Massachusetts, were taken at Masonville Station, Quebec, and at Seabrook, New Hampshire.
Winter.--A few night herons occasionally spend the winter as far north as New England, but most of the birds which breed in the northern States migrate south in the fall to join the resident heron population of the Southland, where they can lead an indolent life of luxurious ease, grow fat, and prepare for the next breeding season.
Black-crowned Night Heron* Nycticorax nycticorax
*Original Source: Bent, Arthur Cleveland. 1927. Smithsonian Institution United States National Museum Bulletin 135: 197-213. United States Government Printing Office