Part 6 (1/2)
The size of an egg is no safe criterion of the size of the bird that laid it, for a large bird may lay a small egg, or a small bird a large one. Comparing the egg of the great Moa with that of our aepyornis one might think the latter much the larger bird, say twelve feet in height, when the facts in the case are that while there was no great difference in the weight of the two, that difference, and a superiority of at least two feet in height, are in favor of the bird that laid the smaller egg.
The record of large eggs, however, belongs to the Apteryx, a New Zealand bird smaller than a hen, though distantly related to the Moas, which lays an egg about one-third of its own weight, measuring 3 by 5 inches; perhaps it is not to be wondered at that the bird lays but two.
Although most of the eggs of these big birds that have been found have literally been unearthed from the muck of swamps, now and then one comes to light in a more interesting manner as, for example, when a perfect egg of aepyornis was found afloat after a hurricane, bobbing serenely up and down with the waves near St. Augustine's Bay, or when an egg of the Moa was exhumed from an ancient Maori grave, where for years it had lain unharmed, safely clasped between the skeleton fingers of the occupant.
So far very few of these huge eggs have made their way to this country, and the only egg of aepyornis now on this side of the water is the property of a private individual.
Most recent in point of discovery, but oldest in point of time, are the giant birds from Patagonia, which are burdened with the name of Phororhacidae, a name that originated in an error, although the error may well be excused. The first fragment of one of these great birds to come to light was a portion of the lower jaw, and this was so ma.s.sive, so un-bird-like, that the finder dubbed it _Phororhacos_, and so it must remain.
[Ill.u.s.tration: Fig. 29.--Eggs of Feathered Giants, aepyornis, Ostrich, Moa, Compared with a Hen's Egg.]
It is a pity that all the large names were used up before this group of birds was discovered, and it is particularly unfortunate that Dinornis, terrible bird, was applied to the root-eating Moas, for these Patagonian birds, with their ma.s.sive limbs, huge heads and hooked beaks, were truly worthy of such a name; and although in nowise related to the eagles, they may in habit have been terrestrial birds of prey. Not all the members of this family are giants, for as in other groups, some are big and some little, but the largest among them might be styled the Daniel Lambert of the feathered race. _Brontornis_, for example, the thunder bird, or as the irreverent translate it, the thundering big bird, had leg-bones larger than those of an ox, the drumstick measuring 30 inches in length by 2-1/2 inches in diameter, or 4-1/4 inches across the ends, while the tarsus, or lower bone of the leg to which the toes are attached, was 16-1/2 inches long and 5-1/2 inches wide where the toes join on. Bear this in mind the next time you see a large turkey, or compare these bones with those of an ostrich: but lest you may forget, it may be said that the same bone of a fourteen-pound turkey is 5-1/2 inches long, and one inch wide at either end, while that of an ostrich measures 19 inches long and 2 inches across the toes, or 3 at the upper end.
If Brontornis was a heavy-limbed bird, he was not without near rivals among the Moas, while the great Phororhacos, one of his contemporaries, was not only nearly as large, but quite unique in build. Imagine a bird seven or eight feet in height from the sole of his big, sharp-clawed feet, to the top of his huge head, poise this head on a neck as thick as that of a horse, arm it with a beak as sharp as an icepick and almost as formidable, and you have a fair idea of this feathered giant of the ancient pampas. The head indeed was truly colossal for that of a bird, measuring 23 inches in length by 7 in depth, while that of the racehorse Lexington, and he was a good-sized horse, measures 22 inches long by 5-1/2 inches deep. The depth of the jaw is omitted because we wish to make as good a case as possible for the bird, and the jaw of a horse is so deep as to give him an undue advantage in that respect.
[Ill.u.s.tration: Fig. 30.--Skull of Phororhacos Compared with that of the Race-horse Lexington.]
We can only speculate on the food of these great birds, and for aught we know to the contrary they may have caught fish, fed upon carrion, or used their powerful feet and huge beaks for grubbing roots; but if they were not more or less carnivorous, preying upon such reptiles, mammals and other birds as came within reach, then nature apparently made a mistake in giving them such a formidable equipment of beak and claw. So far as habits go we might be justified in calling them cursorial birds of prey.
[Ill.u.s.tration: Fig. 31.--Leg of a Horse Compared with that of the Giant Moa.]
We really know very little about these Patagonian giants, but they are interesting not only from their great size and astounding skulls, but because of the early age (Miocene) at which they lived and because in spite of their bulk they are in nowise related to the ostriches, but belong near the heron family. As usual, we have no idea why they became extinct, but in this instance man is guiltless, for they lived and died long before he made his appearance, and the ever-convenient hypothesis ”change of climate” may be responsible for their disappearance.
Something, perhaps, remains to be said concerning the causes which seem to have led to the development of these giant birds, as well as the reasons for their flightless condition and peculiar distribution, for it will be noticed that, with the exception of the African and South American ostriches the great flightless birds as a rule are, and were, confined to uninhabited or spa.r.s.ely populated islands, and this is equally true of the many small, but equally flightless birds. It is a seemingly harsh law of nature that all living beings shall live in a more or less active struggle with each other and with their surroundings, and that those creatures which possess some slight advantage over their fellows in the matter of speed, or strength, or ability to adapt themselves to surrounding conditions, shall prosper at the expense of the others. In the power of flight, birds have a great safeguard against changes of climate with their accompanying variations in the supply of food, and, to a lesser extent, against their various enemies, including man. This power of flight, acquired early in their geological history, has enabled birds to spread over the length and breadth of the globe as no other group of animals has done, and to thrive under the most varying conditions, and it would seem that if this power were lost it must sooner or later work harm. Now to-day we find no great wingless birds in thickly populated regions, or where beasts of prey abound; the ostriches roam the desert wastes of Arabia, Africa and South America where men are few and savage beasts scarce, and against these is placed a fleetness of foot inherited from ancestors who acquired it before man was. The heavy ca.s.sowaries dwell in the thinly inhabited, thickly wooded islands of Malaysia, where again there are no large carnivores and where the dense vegetation is some safeguard against man; the emu comes from the Australian plains, where also there are no four-footed enemies[11] and where his ancestors dwelt in peace before the advent of man. And the same things are true of the Moas, the aepyornithes, the flightless birds of Patagonia, the recent dodo of Mauritius and the solitaire of Rodriguez, each and all of which flourished in places where there were no men and practically no other enemies. Hence we deduce that absence of enemies is the prime factor in the existence of flightless birds,[12] although presence of food is an essential, while isolation, or restriction to a limited area, plays an important part by keeping together those birds, or that race of birds, whose members show a tendency to disuse their wings. It will be seen that such combinations of circ.u.mstances will most naturally be found on islands whose geological history is such that they have had no connection with adjacent continents, or such a very ancient connection that they were not then peopled with beasts of prey, while subsequently their distance from other countries has prevented them from receiving such population by accident in recent times and has also r.e.t.a.r.ded the arrival of man.
[11] _The dingo, or native dog, is not forgotten, but, like man, it is a comparatively recent animal._
[12] _Note that in Tasmania, which is very near Australia, both in s.p.a.ce and in the character of its animals, there are two carnivorous mammals, the Tasmanian ”Wolf” and the Tasmanian Devil, and no flightless birds._
Once established, flightlessness and size play into one another's hands; the flightless bird has no limit placed on its size[13] while granted a food supply and immunity from man; the larger the bird the less the necessity for wings to escape from four-footed foes. So long as the climate was favorable and man absent, the big, clumsy bird might thrive, but upon the coming of man, or in the face of any unfavorable change of climate, he would be at a serious disadvantage and hence whenever either of these two factors has been brought to bear against them the feathered giants have vanished.
[13] _While we do not know the limit of size to a flying creature, none has as yet been found whose wings would spread over twenty feet from tip to tip, and it is evident that wings larger than this would demand great strength for their manipulation._
_REFERENCES_
_There is a fine collection of mounted skeletons of various species of Moas in the Museum of Comparative Zoology at Cambridge, Ma.s.s., and another in the American Museum of Natural History, New York. A few _other skeletons and numerous bones are to be found in other inst.i.tutions, but the author is not aware of any egg being in this country. Specimens of the aepyornis are rare in this country, but Mr.
Robert Gilfort, of Orange, N.J., is the possessor of a very fine egg. A number of eggs have been sold in London, the prices ranging from 200 down to 42, this last being much less than prices paid for eggs of the great auk. But then, the great auk is somewhat of a fad, and there are just enough eggs in existence to bring one into the market every little while. Besides, the number of eggs of the great auk is a fixed quant.i.ty, while no one knows how many more of aepyornis remain to be discovered in the swamps of Madagascar. No specimens of the gigantic Patagonian birds are now in this country, but a fine example of one of the smaller forms, Pelycornis, including the only breast-bone yet found, is in the Museum of Princeton University._
_The largest known tibia of a Moa, the longest bird-bone known, is in the collection of the Canterbury Museum, Christchurch, New Zealand; it is 3 feet 3 inches long. This, however, is exceptional, the measurements of the leg-bones of an ordinary Dinornis maximus being as follows: Femur, 18 inches; tibia, 32 inches; tarsus, 19 inches, a total of 5 feet 9 inches. The egg measures 10-1/2 by 6-1/2 inches._
_There is plenty of literature, and very interesting literature, about the Moas, but, unfortunately, the best of it is not always accessible, being contained in the ”New Zealand Journal of Science” and the ”Transactions of the New Zealand Inst.i.tute.” The volume of ”Transactions” for 1893, being vol. xxvi., contains a very full list of articles relating to the Moas, compiled by Mr. A. Hamilton; it will be found to commence on page 229. There is a good article on Moa in Newton's ”Dictionary of Birds,” a book that should be in every library._
[Ill.u.s.tration: Fig. 32.--The Three Giants, Phororhacos, Moa, Ostrich.]
IX
THE ANCESTRY OF THE HORSE
”_Said the little Eohippus I am going to be a horse And on my middle finger-nails To run my earthly course._”