If we consider that similar bird-republics are to be found on almost every rocky coast or surf-beaten cliff of the northern seas, we must needs be astonished at the inexhaustible prodigality of Nature, which covers desolate rocks with such a profusion of life. The vast number of sea-birds is the more surprising, as many species, such as the guillemot, the auk, the fulmar, and the puffin, lay but one single egg on the naked rock, and often in so precarious a situation, that it is almost inconceivable how breeding can take place. When the birds are surprised and suddenly fly off, many of the eggs tumble down into the surf. Sea-eagles, falcons, and raptorial gulls destroy a great number, and pounce upon the young; thousands fall a prey to the rigours of an Arctic winter; the spring-tides sweeping over low shores, often carry away whole generations at once, and many a maritime population lives entirely upon the sea-fowl that breed upon the sterile soil. And yet, in spite of so many enemies and persecutions, their numbers remain undiminished, nor has their importance ever ceased in the domestic economy of the rude islanders of the north.
Sea-Fowl Shooting.
But however valuable the eggs and the oil, the feathers and the flesh of the hyperborean bird-republics may be to man, they are far from equalling in importance the guano producing sea-fowl of the tropical seas. This inestimable manure, which has become so indispensable to the British agriculturist, is found scattered over numerous localities in the intertropical regions. It abounds on many of the rocky islets of the Red Sea, where the life-teeming waters afford sustenance to innumerable sea-gulls, cormorants, and pelicans; but its most widely celebrated stores cover the small Chincha Islands, not far from Pisco, about a hundred miles to the south of Callao, where they form enormous layers 50 or 60 feet deep.
The upper strata are of a greyish-brown colour, which lower down becomes darker; and in the inferior strata the colour is a rusty red, as if tinged by oxide of iron. The guano becomes progressively more and more compact from the surface downwards, a circumstance naturally accounted for by the gradual deposit of the strata and the increasing superincumbent weight. As is universally known, guano is formed of the excrements of different kinds of marine birds; but the species which Tschudi, the celebrated Peruvian traveller, more particularly enumerates are—Larus modestus (Tschudi), Rhynchops nigra (Linn.), Plotus anhinga (Linn.), Pelecanus thayus (Mol.), Phalacrocorax Gaimardii and albigula (Tsch.), and chiefly the Sula variegata (Tsch.).
The immense flocks of these birds, as they fly along the coast, appear like aërial islands; and when their vast numbers, their extraordinary voracity, and the facility with which they procure their food are considered, we cannot be surprised at the magnitude of the beds of guano which have resulted from the uninterrupted accumulations of countless ages. During the first year of the deposit the strata are white, and the guano is then called Guano blanco. In the opinion of the Peruvian cultivators, this is the most efficacious kind. As soon as the dealers in guano begin to work one of the beds, the island on which it is formed is abandoned by the birds. It has also been remarked that, since the increase of trade and navigation, they have withdrawn from the islands in the neighbourhood of the ports. Under the empire of the Incas, the guano was regarded as an important branch of state economy. It was forbidden, on pain of death, to kill the young birds. Each island had its own inspector, and was assigned to a certain province. The whole distance between Arica and Chaucay, a length of two hundred nautical miles, was exclusively manured with guano. These wise provisions have been entirely forgotten by the Spaniards, but the Peruvians now begin to discover the error of their former masters, and look forward with anxiety to the period when the guano will no longer suffice for the wants of husbandry. At the present day they use it chiefly in the cultivation of maize and potatoes. A few weeks after the seeds begin to shoot, a little hole is made round each root and filled up with guano, which is afterwards covered with a layer of earth. After the lapse of twelve or fifteen hours, the whole field is laid under water, and left in that state for about half a day. Of the guano blanco a less quantity suffices, and the field must be more speedily and abundantly watered, otherwise the roots would be destroyed. The effect of this manure is incredibly rapid. In a few days the growth of the plant is doubled; if the manure is repeated a second time, but in smaller quantity, a rich harvest is certain;—at least the produce will be three times greater than that which would have been obtained from the unmanured soil. The uniformity of climate, along a coast where rain is never known to fall, contributes essentially to the superior quality of the Chincha guano, as atmospherical precipitations naturally dissolve and wash away many of the most fertilising salts.
The consumption of guano in Western Europe, and particularly in England, increases with surprising rapidity. On the island of Iquique a layer thirty feet deep, and covering a space of 220,000 square feet, has been entirely removed within twenty-seven years. In the year 1854, 250,000 tons were dug in the Chincha Islands, and the actual annual exportation amounts to double the quantity. The digestive functions of the Sula and her companions thus bring in larger sums to the Peruvian Government than all the silver mines of Cerro de Pasco, and the transport of the guano employs larger fleets than ever Spain possessed at the brightest period of her power.
"The Chincha Islands," says Castelnau (Expédition dans les Parties Centrales de l'Amérique du Sud; Paris, 1851), "are completely desert and devoid of vegetation; their granite soil is clearly distinguished by its colour from the thick stratum of guano with which it is covered, and the surface of which looks at a distance like snow. The steep banks render landing difficult, but facilitate at the same time the shipping of the produce, as the vessels lie at anchor close to the pits. Digging takes place at three places, close to one another, and the traveller has only to compare the enormous deposits with the smallness of the excavations, which at some distance are hardly perceptible, to convince himself of the inexhaustible supply. Some huts have been constructed on the island, where, in the midst of ammoniacal effluvia, some Peruvian customhouse officers and soldiers superintend the working of the guano-mines."
Birds of Passage.