The cock of the rock, Rupicola crocea, is, on the other hand, an example of a bird having its range defined by a geological formation, and by the physical character of the country. Its range extends in a curving line along the centre of the mountainous district of Guiana, across the sources of the Rio Negro and Orinooko, towards the Andes; it is thus entirely comprised in the granite formation, and in that part of it where there are numerous peaks and rocks, in which the birds make their nests.
Whether it actually reaches the Andes, or occurs in the same district with the allied R. Peruviana, is not known, but personal information obtained in the districts it inhabits, shows that it is confined to the narrow tract I have mentioned, between 1° south and 6° north latitude, and from the mountains of Cayenne to the Andes, south of Bogotá.
Another bird appears bounded by a geological formation. The common red-backed parrot, Psittacus festivus, is found all over the Lower Amazon, but, on ascending the Rio Negro, has its northern limit about St. Isabel, or just where the alluvial country ends and the granite commences; it also extends up the Japura, but does not pass over to the Uaupés, which is all in the granite district.
The fine blue macaw (Ara hyacinthina) inhabits the borders of the hilly country south of the Amazon, from the sea-coast probably up to the Madeira. Below Santarem, it is sometimes found close up to the banks of the Amazon, but is said never to cross that river. Its head-quarters are the upper waters of the Tocantíns, Xingú, and Tapajoz rivers.
As another instance of a bird not crossing the Amazon, I may mention the beautiful curl-crested Araçarí (Pteroglossus Beauharnaisii), which is found on the south side of the Upper Amazon, opposite the Rio Negro, and at Coarí and Ega, but has never been seen on the north side. The green Jacamar of Guiana also (Galbula viridis) occurs all along the north bank of the Amazon, but is not found on the south, where it is replaced by the G. cyanocollis and G. maculicauda, both of which occur in the neighbourhood of Pará.
FOOTNOTES:
[6] As so few Europeans have seen these large serpents, and the very existence of any large enough to swallow a horse or ox is hardly credited, I append the following account by a competent scientific observer, the well-known botanical traveller Dr. Gardner. In his "Travels in Brazil," p. 356, he says:—
"In the marshes of this valley in the province of Goyaz, near Arrayas, the Boa Constrictor is often met with of considerable size; it is not uncommon throughout the whole province, particularly by the wooded margins of lakes, marshes, and streams. Sometimes they attain the enormous length of forty feet: the largest I ever saw was at this place, but it was not alive. Some weeks before our arrival at Safê, the favourite riding horse of Senhor Lagoriva, which had been put out to pasture not far from the house, could not be found, although strict search was made for it all over the Fazenda. Shortly after this, one of his vaqueiros, in going through a wood by the side of a small river, saw an enormous Boa suspended in the fork of a tree which hung over the water; it was dead, but had evidently been floated down alive by a recent flood, and being in an inert state it had not been able to extricate itself from the fork before the waters fell. It was dragged out to the open country by two horses, and was found to measure thirty-seven feet in length; on opening it the bones of a horse in a somewhat broken condition, and the flesh in a half-digested state, were found within it, the bones of the head being uninjured; from these circumstances we concluded that the Boa had devoured the horse entire."