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Show 1870.] LETTER FROM MR. W. H. HUDSON. 87 The following letter, addressed to the Secretary by Mr. William H. Hudson*, was read:- „ _ " Buenos Ayres, Dec. 14, 1869. " M Y D E A R SIR,-Probably I shall not be able to send any more birds to the Smithsonian Institution. The specimens I may find leisure to collect can be disposed of in Buenos Ayres; but should I meet with any thing new I will forwaid it to the Zoological Society of London. I was well pleased with your favour of November 9th, expressing your desire to see m y notes on the birds I have collected ; and should this letter and others I shall shortly send contain any thing of interest I shall be glad. " Though the pampas of this part of the republic are all but entirely bare of trees, the swampy margins of the Rio de la Plata are covered with an almost impenetrable thicket from two to four miles in width. In this wood neither the thorny Curumamnel nor the gigantic Ambu, that flourish on the open plains, are found; but its trees and shrubs and many of its herbs are natives of the northern states of La Plata, the Chaco, and Paraguay. The seeds have been brought from those countries by the river, or on the Camalote-a species of water-lily that grows round the islands of the Parana and its tributaries. These plants accumulate on the water year by year till they form vast floating islands, and are ultimately torn from their moorings by the floods, carried hundreds of miles down the river, and stranded on its low shores. These migratory islands bring with them not only the seeds of northern^ vegetation, but colonies of insects, reptiles, and other animals. I have known the Cierno, Jaguar, Aquard, and Carpincho, and other large mammals, also large Serpents and Alligators, to have been thus brought down and landed within a few miles of the city of Buenos Ayres. Such large animals soon disappear; but smaller ones remain, so that in this forest Snakes and Batrachians are found of different species from those of the neighbouring plains-also insects, whose great size and gaudy colours prove their northern origin. The reptiles maintain their existence apparently within narrow limits ; but many of the insects (particularly the Lepidoptera) become widely distributed, and show, by the dimmer colours and diminished size of many individuals, the modifying influences of climate and other physical conditions. The strips of vegetation stretching so far into this country from the northern wooded regions have also greatly promoted the distribution of birds. " There are but a very few species of true ' Pampas-birds.' This name I apply to Anthus correndera, Centrites niger, the Red-breasted Lark (Teenioptera), and all those kinds especially adapted to the conditions of the Pampa. These species avoid trees, and find their subsistence, roost, and breed on the ground. But the woody fringe to the river above mentioned has served as a grand highway by which most of our small birds have been introduced into this country. * See articles by Messrs. Sclater and Salvin on Mr. Hudson's collections (P. Z. S. 1868, p. 137, 1869, p. 158 and p. 631), and Mr. Hudson's letter (P. Z S 1869, p. 432). |