(VARIEGATED HERON.)
[Plate XVII.]
[Illustration: ARDETTA INVOLUCRIS.]
+Ardetta involucris+, _Scl. et Salv. Nomencl._ p. 125; _iid. P. Z.
S._ 1869, p. 634; _Hudson, P. Z. S._ 1875, p. 624 (Buenos Ayres);
_Durnford, Ibis_, 1877, p. 189, et 1878, p. 62 (Buenos Ayres);
_Gibson, Ibis_, 1880, p. 159 (Buenos Ayres); _Barrows, Auk_,
1884, p. 271 (Entrerios).
_Description._--Above pale fulvous; narrow stripe on the nape black;
front, stripe on the back of the neck, bend of wing, and outer
secondaries chestnut-red; back striped with black; wing-feathers
dark cinereous with red tips: beneath paler, nearly white on the
belly; neck, breast, and flanks with brown stripes, darker in the
centres; bill yellow; feet brown: whole length 13·0 inches, wing
5·0, tail 1·5.
_Hab._ Paraguay and Argentina.
The Variegated Heron is the least of the family to which it belongs, its
body being no bigger than that of the Common Snipe; but in structure
it is like other Herons, except that its legs are a trifle shorter in
proportion to its size and its wings very much shorter than in other
species. The under plumage is dull yellow in colour, while all the other
parts are variegated with marks of fuscous and various shades of brown
and yellow. The body is extremely slim, and the lower portion of the
neck covered with thick plumage, giving that part a deceptively massive
appearance. The perching faculty, possessed in so eminent a degree by
all Herons, probably attains its greatest perfection in this species,
and is combined with locomotion in a unique and wonderful manner. It
inhabits beds of rushes growing in rather deep water; very seldom, and
probably only accidentally, does it visit the shore, and only when
driven up does it rise above the rushes; for its flight, unlike that of
its congeners, is extremely feeble. The rushes it lives amongst rise,
smooth as a polished pipe-stem, vertically from water too deep for the
bird to wade in; yet it goes up to the summit and down to the surface,
moving freely and briskly about amongst them, or runs in a straight line
through them almost as rapidly as a Plover can run over the bare level
ground. Unless I myself had been a witness of this feat, I could
scarcely have credited it; for how does it manage to grasp the smooth
vertical stems quickly and firmly enough to progress so rapidly without
ever slipping down through them?
The Variegated Heron is a silent solitary bird, found everywhere in the
marshes along the Plata, as also in the reed-beds scattered over the
pampas. It breeds amongst the rushes, and lays from three to five
spherical eggs, of a rich lively green and beautiful beyond comparison.
The nest is a slight platform structure about a foot above the water,
and so small that there is barely space enough on it for the eggs, which
are large for the bird. When one looks down on them they cover and hide
the slight nest, and being green like the surrounding rushes they are
not easy to detect.
When driven up the bird flies eighty or a hundred yards away, and drops
again amongst the rushes; it is difficult to flush it a second time, and
a third time it is impossible. A curious circumstance is that where
it finally settles it can never be found. As I could never succeed in
getting specimens when I wanted them, I once employed some Gaucho boys,
who had dogs trained to hunt young Ducks, to try for this little Heron.
They procured several specimens, and said that without the aid of their
dogs they could never succeed in finding a bird, though they always
marked the exact spot where it alighted. This I attributed to the
slender figure it makes, and to the colour of the plumage so closely
assimilating to that of the dead yellow and brown-spotted rushes always
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 colour far more advantageous than they could be of
themselves.
One day in November 1870, when out shooting, I noticed a Variegated
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
researching 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 on a reed, no 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 his feet to the tip of his
beak, a perceptible curve or inequality, but the whole was the figure
(the exact counterpart) of a straight tapering rush: the loose plumage
arranged to fill inequalities, and 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-coloured 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 of
the blade-like body before me, corresponded so exactly with my own that
I almost doubted that I had moved at all. No sooner had I seen the
finishing part of this marvellous instinct of self-preservation (this
last act making the whole complete), 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
wilderness, and many and perfect as are the instances of adaptation I
have witnessed. I could not finish admiring, and thought that never had
anything so beautiful fallen in my way before; for even the sublime
cloud-seeking instinct of the White Egret and the typical Herons seemed
less admirable than this; and for some time I continued experimenting,
pressing down the bird's head and trying to bend him by main force into
some other position; but the strange rigidity remained unrelaxed, the
fixed attitude unchanged. I also found, as I walked round him, that, as
soon as I got to the opposite side and he could no longer twist himself
on his perch, he whirled his body with great rapidity the other way,
instantly presenting the same front as before.
Finally I plucked him forcibly from the rush and perched him on my hand,
upon which he flew away; but he flew only fifty or sixty yards off,
and dropped into the dry grass. Here he again put in practice the same
instinct so ably that I groped about for ten or twelve minutes before
refinding him, and was astonished that a creature to all appearance so
weak and frail should have strength and endurance sufficient to keep its
body rigid and in one attitude for so long a time.
Our figure of this species (Plate XVII.) is taken from a skin in
Sclater's collection, which was procured by Mr. F. Withington in the
Lomas de Zamora in 1883.