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Show 1870.] LETTER FROM MR. W. H. HUDSON. 801 ances sounding not unlike the distant". baying of a ' deep-mouthed' watch-dog. " The late great increase of the large Owls in this neighbourhood can only be ascribed to the recent cultivation of the plains near the city. Within the last six years a great extent of hitherto bald shelterless grounds have been enclosed, and are now yearly planted with wheat and maize; in the fields the Owls find shelter, and their favourite food in abundance, Mice, Partridges, &c. " The Lechuson frequenting open plains in preference to woods, and hiding by day on the ground, has the colour of its plumage adapted to a country like the desert pampas, rough with a brown vegetation. But the introduction and increase of Sheep quickly changed the aspect of a vast extent of the plain; the long brown grasses disappeared, their place being taken by a tender herbage, short and brilliant green; the country was thus unfitted for their pasturage. All the wild animals have, no doubt, been greatly affected by this sudden change in vegetation and total destruction of cover. But cultivation has now partially restored the physical conditions necessary to the preservation and increase of many species like the Lechuson. In future descriptions I shall frequently refer to these changes on tbe pampas. " The gradual increase or diminution constantly going on in many species about us is little remarked; but the sudden appearance in vast numbers of a species not usually common is regarded by all with interest and wonder. When, owing to a season favourable to propagation, a small species multiplies greatly (as often happens here with Mice, Toads, Crickets, & c ) , we may confidently look for the appearing of multitudes of those birds that subsist on them. Thus, in the year 1856, when the earth swarmed with Mice, vast numbers of the then scarce Lechuson, and flocks of the Great Adjutant Stork (Mycteria americana) also appeared. Armies of these majestic white birds were seen stalking over the grass on all sides, or at the close of day winging their flight to the distant watercourses in a continuous flock ; while the night air resounded to the solemn hoot-ings of the innumerable Owls. However simple may be the cause of the first phenomenon (the sudden great increase of a species incapable of migration but exceedingly prolific), the attendant one appears to have been remarked with astonishment from very early times, and to have given rise to many conjectures. Pliny, if I remember right, relates that one season in some part of Asia Minor the Mice increased in an extraordinary manner, but soon appeared 'an army of strangely painted birds' and devoured them all. Birds of prey and those that subsist on large insects, and possess great powers of flight, without being strictly migratory, when not occupied with the business of propagation, are incessantly wandering in quest of food. They often fly high, and traverse vast distances. When the natural food of any one of such species abounds very much in a particular region, all the birds that discover it remain in it and continually attract to them all of their kind passing over them. It |
