and active and both inquisitive and daring, and they have a very curious dance custom. No man need look for them. They will look for him, and when they find him they will fairly yell the discovery to the universe. In the marshes of the lower Parana I saw flocks of scarlet- headed blackbirds on the tops of the reeds; the females are as strikingly colored as the males, and their jet-black bodies and brilliant red heads make it impossible for them to escape observation among their natural surroundings. On the plains to the west I saw flocks of the beautiful rose-breasted starlings; unlike the red-headed blackbirds, which seemed fairly to court attention, these starlings sought to escape observation by crouching on the ground so that their red breasts were hidden. There were yellow-shouldered blackbirds in wet places, and cow-buntings abounded.
But the most conspicuous birds I saw were members of the family of tyrant flycatchers, of which our own king-bird is the most familiar example. This family is very numerously represented in Argentina, both in species and individuals. Some of the species are so striking, both in color and habits, and in one case also in shape, as to attract the attention of even the unobservant. The least conspicuous, and nevertheless very conspicuous, among those that I saw was the bientevido, which is brown above, yellow beneath, with a boldly marked black and white head, and a yellow crest. It is very noisy, is common in the neighborhood of houses, and builds a big domed nest. It is really a big, heavy kingbird, fiercer and more powerful than any northern kingbird. I saw them assail not only the big but the small hawks with fearlessness, driving them in headlong flight. They not only capture insects, but pounce on mice, small frogs, lizards, and little snakes, rob birds' nests of the fledgling young, and catch tadpoles and even small fish.
Two of the tyrants which I observed are like two with which I grew fairly familiar in Texas. The scissor-tail is common throughout the open country, and the long tail feathers, which seem at times to hamper its flight, attract attention whether the bird is in flight or perched on a tree. It has a habit of occasionally soaring into the air and descending in loops and spirals. The scarlet tyrant I saw in the orchards and gardens. The male is a fascinating little bird, coal- black above, while his crested head and the body beneath are brilliant scarlet. He utters his rapid, low-voiced musical trill in the air, rising with fluttering wings to a height of a hundred feet, hovering while he sings, and then falling back to earth. The color of the bird and the character of his performance attract the attention of every observer, bird, beast, or man, within reach of vision.
The red-backed tyrant is utterly unlike any of his kind in the United States, and until I looked him up in Sclater and Hudson's ornithology I never dreamed that he belonged to this family. He—for only the male is so brightly colored—is coal-black with a dull-red back. I saw these birds on December 1 near Barilloche, out on the bare Patagonian plains. They behaved like pipits or longspurs, running actively over the ground in the same manner and showing the same restlessness and the same kind of flight. But whereas pipits are inconspicuous, the red-backs at once attracted attention by the contrast between their bold coloring and the grayish or yellowish tones of the ground along which they ran. The silver-bill tyrant, however, is much more conspicuous; I saw it in the same neighborhood as the red-back and also in many other places. The male is jet-black, with white bill and wings. He runs about on the ground like a pipit, but also frequently perches on some bush to go through a strange flight-song performance. He perches motionless, bolt upright, and even then his black coloring advertises him for a quarter of a mile round about. But every few minutes he springs up into the air to the height of twenty or thirty feet, the white wings flashing in contrast to the black body, screams and gyrates, and then instantly returns to his former post and resumes his erect pose of waiting. It is hard to imagine a more conspicuous bird than the silver-bill; but the next and last tyrant flycatcher of which I shall speak possesses on the whole the most advertising coloration of any small bird I have ever seen in the open country, and moreover this advertising coloration exists in both sexes and throughout the year. It is a brilliant white, all over, except the long wing-quills and the ends of the tail-feathers, which are black. The first one I saw, at a very long distance, I thought must be an albino. It perches on the top of a bush or tree watching for its prey, and it shines in the sun like a silver mirror. Every hawk, cat, or man must see it; no one can help seeing it.
These common Argentine birds, most of them of the open country, and all of them with a strikingly advertising coloration, are interesting because of their beauty and their habits. They are also interesting because they offer such illuminating examples of the truth that many of the most common and successful birds not merely lack a concealing coloration, but possess a coloration which is in the highest degree revealing. The coloration and the habits of most of these birds are such that every hawk or other foe that can see at all must have its attention attracted to them. Evidently in their cases neither the coloration nor any habit of concealment based on the coloration is a survival factor, and this although they live in a land teeming with bird-eating hawks. Among the higher vertebrates there are many known factors which have influence, some in one set of cases, some in another set of cases, in the development and preservation of species. Courage, intelligence, adaptability, prowess, bodily vigor, speed, alertness, ability to hide, ability to build structures which will protect the young while they are helpless, fecundity—all, and many more like them, have their several places; and behind all these visible causes there are at work other and often more potent causes of which as yet science can say nothing. Some species owe much to a given attribute which may be wholly lacking in influence on other species; and every one of the attributes above enumerated is a survival factor in some species, while in others it has no survival value whatever, and in yet others, although of benefit, it is not of sufficient benefit to offset the benefit conferred on foes or rivals by totally different attributes. Intelligence, for instance, is of course a survival factor; but to-day there exist multitudes of animals with very little intelligence which have persisted through immense periods of geologic time either unchanged or else without any change in the direction of increased intelligence; and during their species-life they have witnessed the death of countless other species of far greater intelligence but in other ways less adapted to succeed in the environmental complex. The same statement can be made of all the many, many other known factors in development, from fecundity to concealing coloration; and behind them lie forces as to which we veil our ignorance by the use of high-sounding nomenclature—as when we use such a convenient but far from satisfactory term as orthogenesis.
II. UP THE PARAGUAY
On the afternoon of December 9 we left the attractive and picturesque city of Asuncion to ascend the Paraguay. With generous courtesy the Paraguayan Government had put at my disposal the gunboat-yacht of the President himself, a most comfortable river steamer, and so the opening days of our trip were pleasant in every way. The food was good, our quarters were clean, we slept well, below or on deck, usually without our mosquito-nettings, and in daytime the deck was pleasant under the awnings. It was hot, of course, but we were dressed suitably in our exploring and hunting clothes and did not mind the heat. The river was low, for there had been dry weather for some weeks —judging from the vague and contradictory information I received there is much elasticity to the terms wet season and dry season at this part of the Paraguay. Under the brilliant sky we steamed steadily up the mighty river; the sunset was glorious as we leaned on the port railing; and after nightfall the moon, nearly full and hanging high in the heavens, turned the water to shimmering radiance. On the mud-flats and sandbars, and among the green rushes of the bays and inlets, were stately water-fowl; crimson flamingoes and rosy spoonbills, dark- colored ibis and white storks with black wings. Darters, with snakelike necks and pointed bills, perched in the trees on the brink of the river. Snowy egrets flapped across the marshes. Caymans were common, and differed from the crocodiles we had seen in Africa in two points: they were not alarmed by the report of a rifle when fired at, and they lay with the head raised instead of stretched along the sand.
For three days, as we steamed northward toward the Tropic of Capricorn, and then passed it, we were within the Republic of Paraguay. On our right, to the east, there was a fairly well-settled country, where bananas and oranges were cultivated and other crops of hot countries raised. On the banks we passed an occasional small town, or saw a ranch-house close to the river's brink, or stopped for wood at some little settlement. Across the river to the west
